defconfig: msm8960: Disable USB Storage debug config

when USB_STORAGE_DEBUG config is enabled, all scsi commands sent to
USB storage devices are printed onto console.  As serial console
is enabled, this is degrading throughput.  This debug feature is
useful only during debugging issues.  Hence disable this feature
by default.

(cherry picked from commit 4713b9d5ded96679e68efdaebe9e8eb0e77b0e6f)
CRs-Fixed: 421411

Change-Id: I0e7e5546af84bbe7a0172fb177d1d3607f858e24
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Neha Pandey <nehap@codeaurora.org>