greybus: gb-beagleplay: Add error handling for gb_greybus_init

greybus: gb-beagleplay: Add error handling for gb_greybus_init

Add error handling for the gb_greybus_init(bg) function call
during the firmware reflash process to maintain consistency
in error handling throughout the codebase. If initialization
fails, log an error and return FW_UPLOAD_ERR_RW_ERROR.

Fixes: 0cf7befa3ea2 ("greybus: gb-beagleplay: Add firmware upload API")
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
Reviewed-by: Ayush Singh <ayush@beagleboard.org>
Link: https://lore.kernel.org/r/20250120140547.1460-1-vulab@iscas.ac.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>