usb: ks_bridge: Limit write size to 16KB

The user space application writes in 1MB chunks while loading MDM
images.  The current code allocate as many bytes as user space
passed to write system call.  These allocations are failing under
memory fragmentation scenario.  Hence limit write size to 16KB.

CRs-Fixed: 434638
(cherry picked from commit 7fcc7799af7ace4c4eda229b0eac6448f98d6637)

Conflicts:

	drivers/usb/misc/ks_bridge.c

Change-Id: I224cf201d724642f99e29874c4c5366ad773131e
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>