Be more precise on deciding whether to call m8xx_ide_init() at
m8xx_setup.c:platform_init().

Compilation fails if CONFIG_BLK_DEV_IDE is defined but
CONFIG_BLK_DEV_MPC8xx_IDE isnt.
Signed-off-by: Marcelo Tosatti <marcelo.tosatti@cyclades.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>