remove mca_is_adapter_used()

Remove the no longer used mca_is_adapter_used().

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>