fs/compat_ioctl.c: fix build error when !BLOCK

No driver uses SG_SET_TRANSFORM any more in Linux, since the ide-scsi
driver was removed in 2.6.29. The compat-ioctl cleanup series moved
the handling for this around, which broke building without CONFIG_BLOCK.

Just remove the code handling it for compat mode.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>