uml: fix CONFIG_RAW dependencies

Add the BLOCK dependency for RAW_DRIVER, to match what's in
drivers/char/Kconfig.  Also, while we're there, update the alleged
obsolesence of RAW_DRIVER since it doesn't seem to be going away any
time soon.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>