Import unified.h from Linux kernel 4.4.6 , commit
0d1912303e54ed1b2a371be0bba51c384dd57326 . This header file contains
macros used in libgcc functions in Linux kernel on ARM and will be
needed for the libgcc sync.

Since unified.h defines the W(instr) macro, we must drop this from
the macro from memcpy.S , otherwise this triggers a warning about
symbol redefinition. In order to keep the changes to unified.h to
the minimum, tweak arch/arm/lib/Makefile such that it defines the
CONFIG_ARM_ASM_UNIFIED macro, which places .syntax unified into all
of the assembler files. This is mandatory.

Moreover, for Thumb2 build, define CONFIG_THUMB2_KERNEL macro if and
only if Thumb2 build is enabled. This macro is checked by unified.h
and toggles between ARM and Thumb2 variant of the instructions in the
assembler source files.

Finally, this patch defines __LINUX_ARM_ARCH__=N macro based on the
new CONFIG_SYS_ARM_ARCH Kconfig option. This macro selects between
more optimal and more dense codepaths which work on armv5 and newer
and less optimal codepaths which work on armv4 and possible armv3m.
Tegra2 needs the same special handling as it does in arch/arm/Makefile
to cater for the arm720t boot core.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>