At present two acpi files are built every time since they use a version
number from version.h

This is not necessary. Make use of the same technique as for the version
string, so that they are build only when they change.

Signed-off-by: Simon Glass <sjg@chromium.org>

More C files do not use compile time timestamp macros and do not have to be
recompiled every time when SOURCE_DATE_EPOCH changes.

This patch moves version_string[] from version.h to version_string.h and
updates other C files which only needs version_string[] string to include
version_string.h instead of version.h. After applying this patch these
files are not recompiled every time when SOURCE_DATE_EPOCH changes.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Tom Rini <trini@konsulko.com>