staging: vchiq_arm: Improve error log for vchiq_platform_init

staging: vchiq_arm: Improve error log for vchiq_platform_init

During sending the base address of the slots to the VideoCore
firmware via mailbox property, issues could happened on the ARM
and on the VideoCore side. So better separate the error handling
in order to provide more details. This should help to narrow
down the possible cause.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Link: https://lore.kernel.org/r/20230123191629.21019-1-stefan.wahren@i2se.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>