firmware: Fix missing inline

firmware: Fix missing inline

I mistakenly dropped the inline while resolving the patch conflicts in
the previous fix patch.  Without inline, we get compiler warnings wrt
unused functions.

Note that Mauro's original patch contained the correct changes; it's
all my fault to submit a patch before a morning coffee.

Fixes: c8917b8ff09e ("firmware: fix build errors in paged buffer handling code")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20190723081159.22624-1-tiwai@suse.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>