mini-os: arm: scheduling

Based on an initial patch by Karim Raslan.

Signed-off-by: Karim Allah Ahmed <karim.allah.ahmed@gmail.com>
Signed-off-by: Thomas Leonard <talex5@gmail.com>

---
Changes since v6:

Addressed Ian Campbell's points:
- replace "mov pc" with "bx"
- preserve all callee-saved registers on context switch
mini-os: arm: events

Signed-off-by: Karim Allah Ahmed <karim.allah.ahmed@gmail.com>
Signed-off-by: Thomas Leonard <talex5@gmail.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
mini-os: arm: time

Based on an initial patch by Karim Raslan.

Signed-off-by: Karim Allah Ahmed <karim.allah.ahmed@gmail.com>
Signed-off-by: Thomas Leonard <talex5@gmail.com>

---

Addressed Julien Grall's comments:
- Remove wall-clock time support (doesn't work on ARM anyway)
mini-os: arm: interrupt controller

Based on an initial patch by Karim Raslan.

Signed-off-by: Karim Allah Ahmed <karim.allah.ahmed@gmail.com>
Signed-off-by: Thomas Leonard <talex5@gmail.com>

---

Changes since v6:

Addressed Julien Grall's comments:
- converted ?: to if
mini-os: arm: build system

Based on an initial patch by Karim Raslan.

This activates the ARM code added in the previous patches. On ARM,
Mini-OS will boot and display some output on the console. Tested with:

make XEN_TARGET_ARCH=arm32 CROSS_COMPILE=arm-linux-gnueabihf- \
	CONFIG_TEST=y CONFIG_START_NETWORK=n CONFIG_BLKFRONT=n \
	CONFIG_NETFRONT=n CONFIG_FBFRONT=n CONFIG_KBDFRONT=n \
	CONFIG_CONSFRONT=n CONFIG_XC=n -j4

The memmove implementation is from FreeBSD's
contrib/ldns/compat/memmove.c (r246827).

The change to fdt_ro.c is to avoid a compiler warning.

Signed-off-by: Karim Allah Ahmed <karim.allah.ahmed@gmail.com>
Signed-off-by: Thomas Leonard <talex5@gmail.com>

---

Changes since v6:

- Use Xen's existing copy of libfdt instead of including our own copy.
- Only build libfdt with read support, since that's all we need.
mini-os: arm: show registers, stack and exception vector on fault

Signed-off-by: Thomas Leonard <talex5@gmail.com>

---

Exit with SHUTDOWN_crash on BUG or fault (suggested by Ian Campbell).
mini-os: fixed compiling with debug=n

Without -fno-tree-loop-distribute-patterns, gcc -O3 recognises that our
"memset" is doing a memset operation and tries to make it call the
standard "memset", creating a loop.

The change to fdt_ro.c is to avoid a compiler warning.

Signed-off-by: Thomas Leonard <talex5@gmail.com>