uboot-phytec

remoteproc: ipu: Fix return error in probe

load_firmware returns an error value when there is no firmware. But
probe looks only for a zero value for success. So if there is no
firmware, ipu_probe still return success. Fix it by returning an error
value in case of no firmware.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>