usb: usb_bam: Fix issue for not checking NULL returned value

Ensure to correctly check the right pointer returned
from a call to function platform_get_resource_byname()
in order to prevent accessing this pointer afterwards
in case this pointer is NULL.

Change-Id: I8f6ba2944a4c60d2b4e668686c8bf7bc2640f46b
CRs-Fixed: 535640
Signed-off-by: Ido Shayevitz <idos@codeaurora.org>