firmware_class: Introduce the request_firmware_direct API

On devices with low memory, using request_firmware on rather
large firmware images results in a memory usage penalty that
might be unaffordable. Introduce a new API that allows the
firmware image to be directly loaded to a destination address
without using any intermediate buffer.

Change-Id: I3ac3c5036c14773125291eccf83d494a8703b4cd
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>