media: mc/Kconfig: remove staging dependency for request API

When the request API got merged, only drivers at staging were
using it. As we wanted to be able to do future changes on it,
we added an artificial depends on STAGING_MEDIA.

Yet, request API is there for quite some time now, and
didn't suffer any API breakages during this time. So, drop
this.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Suggested-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>