remoteproc: uclass: Add methods to load firmware to rproc and boot rproc

Add APIs to set a firmware_name to a rproc and boot the rproc with the
same firmware.

Clients can call rproc_set_firmware() API to set firmware_name for a rproc
whereas rproc_boot() will load the firmware set by rproc_set_firmware() to
a buffer by calling request_firmware_into_buf(). rproc_boot() will then
load the firmware file to the remote processor and start the remote
processor.

Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Acked-by: Ravi Gunasekaran <r-gunasekaran@ti.com>
Reviewed-by: Roger Quadros <rogerq@kernel.org>