ARM: 9311/1: decompressor: move function prototypes to misc.h

A number of prototypes are missing for the decompressor, some
of them are in the .c files that contain the callers, but are
invisible at the function definition:

arch/arm/boot/compressed/misc.c:129:17: error: no previous prototype for '__div0' [-Werror=missing-prototypes]
arch/arm/boot/compressed/misc.c:138:1: error: no previous prototype for 'decompress_kernel' [-Werror=missing-prototypes]
arch/arm/boot/compressed/misc.c:163:6: error: no previous prototype for 'fortify_panic' [-Werror=missing-prototypes]
arch/arm/boot/compressed/decompress.c:63:5: error: no previous prototype for 'do_decompress' [-Werror=missing-prototypes]
arch/arm/boot/compressed/fdt_check_mem_start.c:63:10: error: no previous prototype for 'fdt_check_mem_start' [-Werror=missing-prototypes]

Move these all to misc.h so they are visible by the callee as well.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>