ARM: 9035/1: uncompress: Add be32tocpu macro

DTB stores all values as 32-bit big-endian integers.
Add a macro to convert such values to native CPU endianness, to reduce
duplication.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>