Fix error handling in HDIO_GETGEO compat wrapper

Don't clobber error from sys_ioctl in HDIO_GETGEO compat wrapper.

Signed-off-by: Andreas Schwab <schwab@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>