gdc: fix gdc coverity issue [1/1]

gdc: fix gdc coverity issue [1/1]

PD#SWPL-13979

Problem:
coverity defect cleanup for gdc

Solution:
DEADCODE on aml_dmabuf_ops_attach()
RESOURCE_LEAK on aml_dma_alloc()
REVERSE_INULL on aml_dma_mmap()
USE_AFTER_FREE on aml_dma_put()
CHECKED_RETURN on gdc_platform_probe()
FORWARD_NULL on gdc_process_ex_info()/gdc_process_with_fw()
UNINIT on gdc_process_ex_info()/gdc_process_with_fw()
NO_EFFECT on gdc_log()

Verify:
coverity check

Change-Id: Iafd7eb5f74792300c68c50ffc5d0e36063cce906
Signed-off-by: Cao Jian <jian.cao@amlogic.com>
(cherry picked from commit b28a8ac621c428437199386895a7ac3012e52905)