drivers/block/Kconfig: update RAM block device module name
RAM block device support module name changed to brd.ko some years ago
with an "rd" alias to match previous module implementation. This patch
updates its Kconfig definition.
Signed-off-by: Fabian Frederick <fabf@skynet.be> Acked-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>