firmware: fix the request_firmware() dummy

> the build (.config attached) failed, make ends with :
> ...
>   UPD     include/linux/compile.h
>   CC      init/version.o
>   LD      init/built-in.o
>   LD      vmlinux
> drivers/built-in.o: In function `sas_request_addr':
> (.text+0x33bab): undefined reference to `request_firmware'
> drivers/built-in.o: In function `sas_request_addr':
> (.text+0x33c3f): undefined reference to `release_firmware'
> make: *** [vmlinux] Error 1

There's a slight fault in the stub logic.  It fails for FW_LOADER=m and
the user =y.

This should fix it.

This patch fixes the following 2.6.26-rc regression:
  http://bugzilla.kernel.org/show_bug.cgi?id=10730



Reviewed-by: Toralf Foerster <toralf.foerster@gmx.de>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>