test_firmware: add support for request_firmware_into_buf

Add test config into_buf to allow request_firmware_into_buf to be
called instead of request_firmware/request_firmware_direct.  The number
of parameters differ calling request_firmware_into_buf and support
has not been added to test such api in test_firmware until now.

Signed-off-by: Scott Branden <scott.branden@broadcom.com>
Acked-by: Luis Chamberlain <mcgrof@kernel.org>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20190822184005.901-2-scott.branden@broadcom.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>