usb: ks_bridge: Add debug logs for ks_bridge Tx data path

Add debug events in Tx path to determine if the data is sent
from ks to mdm. The current code only logs Tx URB submit event
and there is a possibility of URB submission failure.

CRs-Fixed: 630240
Change-Id: I17a6313f297048a5eec11da57b86f07708d093b5
Signed-off-by: ChandanaKishori Chiluveru <cchilu@codeaurora.org>