arm: Switch to -mno-unaligned-access when supported by the compiler

When we tell the compiler to optimize for ARMv7 (and ARMv6 for that
matter) it assumes a default of SCTRL.A being cleared and unaligned
accesses being allowed and fast at the hardware level.  We set this bit
and must pass along -mno-unaligned-access so that the compiler will
still breakdown accesses and not trigger a data abort.

To better help understand the requirements of the project with respect
to unaligned memory access, the
Documentation/unaligned-memory-access.txt file has been added as
doc/README.unaligned-memory-access.txt and is taken from the v3.14-rc1
tag of the kernel.

Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Cc: Mans Rullgard <mans@mansr.com>
Signed-off-by: Tom Rini <trini@ti.com>

fs/ubifs/Makefile

@@ -13,6 +13,3 @@ obj-y := ubifs.o io.o super.o sb.o master.o lpt.o
 obj-y += lpt_commit.o scan.o lprops.o
 obj-y += tnc.o tnc_misc.o debug.o crc16.o budget.o
 obj-y += log.o orphan.o recovery.o replay.o
-
-# SEE README.arm-unaligned-accesses
-CFLAGS_super.o := $(PLATFORM_NO_UNALIGNED)