Bring defconfig up to date.

Also disable CONFIG_BLK_DEV_UBD_SYNC by default.  By performing synchronous
I/O to the host, it slows things down, only protects against host crashes, and
can make a UML appear to hang while it waits for the host's disk.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>