simtec: Fix typo in pm-simtec.c

Correct spelling "Manangement" to "Management" in
arch/arm/plat-s3c24xx/pm-simtec.c

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>