wdc: Fix use-after-free access of cbs_data

wdc: Fix use-after-free access of cbs_data

Fix incorrect access after memory is already freed up. Also couple
of minor fixes to use correct cpu endianness while accessing data
read from drive.

Create a new function wdc_get_fw_cust_id that will simplfy the code
and handle the free of the allocated data

Signed-off-by: Jeff Lien <jeff.lien@wdc.com>
Co-Authored-by: Indraneel-M
[dwagner: updated commit message and merged everything into one patch]
Signed-off-by: Daniel Wagner <dwagner@suse.de>