ARM: tegra: rework boot scripts

Update the common Tegra boot scripts in the default environment to

a) Make use of the new "test -e" shell command to avoid some error
   messages.

b) Allow booting using the sysboot command and extlinux.conf. This
   allows easy creation of boot menus, and provides a simple interface
   for distros to parameterize/configure the boot process.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
v5:
* For sysboot, use ${prefix}extlinux/extlinux.conf,
  not ${prefix}extlinux.conf, to match existing config generators.
v4:
* Prioritize extlinux.conf over boot.scr.uimg when searching; it makes
  sense to use the cross-distro/-bootloader (hopeful) standard first.
* Replace ; in the middle of echo'd text in boot scripts.
* Add missing space between commands in boot scripts.
* s/exists/test -e/ in commmit description.
v3: s/exists/test -e/ in shell commands.
v2: No change.
ARM: tegra: implement bootcmd_pxe

This retrieves a PXE config file over the network, and executes it. This
allows an extlinux config file  to be retrieved over the network and
executed, whereas the existing bootcmd_dhcp retrieves a U-Boot script.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
v4: No change.
v3: No change.
v2: No change.
ARM: tegra: set CONFIG_SYS_USB_EHCI_MAX_ROOT_PORTS

Tegra's EHCI controllers only have a single PORTSC register. Configure
U-Boot to know this. This prevents e.g. ehci_shutdown() from touching
non-existent registers.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
LATER: ARM: tegra: add support for more clocks on Tegra114

FIXME: work on this later after Tegra124 support.
FIXME: re-write commit description now it's been split up...

Some Tegra114 peripherals can take up to 8 different clock sources
(parents), including 4 new ones that don't exist on previous chips
(PLLC2/C3/MEM2/SRC2). Expand clock/PLL code/tables to support these
additional bits/sources.

Changes were made to some common code. Testing on Tegra30 and Tegra20
showed no changes in periph clock sources/divisors.

Also, peripheral clock sources that no longer exist on Tegra114 were
removed from the clock_periph_type table (CVE, TVDAC, etc.), and periphs
that are gone or not needed in early init are no longer brought out of
reset/enabled (FUSE, IRAMA/B/C/D, etc.).

Signed-off-by: Tom Warren <twarren@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
v3:
* Undid change to assert on divisor value; the fix was applied to the
  wrong assert. The assert which should have been fixed was within the
  removed unused code.
v2:
- Fixed an assert test for a divisor value (s/b >0, not >=0)
- Remove some unused code
Revert "LATER: ARM: tegra: add support for more clocks on Tegra114"

This reverts commit 6cf0329f447d51e1ad5909d46f79cfd4756a4c93.
LATER: ARM: tegra: dalmore: add PMIC init for various peripherals

FIXME: work on this later after Tegra124 support.

These power rails are currently needed for kernel boot. This will be move
to a PMIC-specific driver (or even better moved to the kernel) at a later
date.

Signed-off-by: Tom Warren <twarren@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Revert "LATER: ARM: tegra: dalmore: add PMIC init for various peripherals"

This reverts commit 2e5b746676e5360325456184750e979726b4a009.