init: Declare rodata_enabled and mark_rodata_ro() at all time

Declaring rodata_enabled and mark_rodata_ro() at all time
helps removing related #ifdefery in C files.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>