firmware_loader: remove #include <generated/utsrelease.h>

utsrelease.h is potentially generated on each build.
By removing this unused include we can get rid of some spurious
recompilations.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Russ Weight <russell.h.weight@intel.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>