vexpress64: kconfig: consolidate CONFIG_TARGET_VEXPRESS_AEMV8A_SEMI

We do not have to distinguish CONFIG_TARGET_VEXPRESS_AEMV8A_SEMI
from CONFIG_TARGET_VEXPRESS_AEMV8A.  Rename the former to the latter.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: David Feng <fenghua@phytium.com.cn>
Cc: Steve Rae <srae@broadcom.com>
kconfig: armv8: move CONFIG_ARM64 to Kconfig

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
arm: debug: import debug files from Linux 3.16

U-Boot does not have arch/arm/kernel, include/uapi directories,
This commit copies files as follows:

  Location in Linux               -> Location in U-Boot

  arch/arm/kernel/debug.S         -> arch/arm/lib/debug.S
  arch/arm/include/debug/8250.S   -> arch/arm/include/debug/8250.S
  include/uapi/linux/serial_reg.h -> include/linux/serial_reg.h

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
arm: debug: add Kconfig entries for lowlevel debug

We have not had a good method to debug the early boot stage such as
lowlevel_init function.  I guess developers generally use dedicated
debuggers for that, but it is difficult in some cases.
(For example, my debugger cannot connect to the ARM processor when
it is in the secure state.  It sometimes happens when I need to
debug the early boot stage on ARM SoCs with secure extension.)

The low level debug feature in Linux would be also helpful for U-boot
when we are stucking in nasty problems where the console is not
available yet.

You have to enable CONFIG_DEBUG_LL to use this feature.
For now, only 8250-compatible UART devices are supported.
You can add a header file under arch/arm/include/debug/ directory
to support your UART device if necessary.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cover-letter:
Introduce low-level debug for ARM architecture

I have been in trouble for a while to debug some nasty problem
where neighter a debugger nor printf() function is available.

I found the lowlevel debug feature in ARM Linux can be used as is
in U-Boot too.

I tested this series on our SoCs (32bit ARM, specificly Coretex-A9).
Because I was not sure about aarch64, I have this feature
depend on "! ARM64".

1/4 and 2/4 refactor a bit and move CONFIG_ARM64 to Kconfig.

3/4 imports some source files from Linux 3.16 and
4/4 adds the Kconfig menu.

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