misc: fs_loader: Use buffer pointer in request_firmware_into_buf_via_script()

misc: fs_loader: Use buffer pointer in request_firmware_into_buf_via_script()

Use plain buffer pointer in request_firmware_into_buf_via_script()
instead of a pointer to pointer. The later is not necessary as the
request_firmware_into_buf_via_script() does not modify the buffer
pointer. Update the mediatek driver to match.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Weijie Gao <weijie.gao@mediatek.com>