USB: gadget: Cleanup boot-up message with default usb composition

The print message with rmnet bind and adb_bind is enabled by default.
It appears for each default composition switch. Watchdog timeout is
seen if there is stability issue on device bootup with serial console
enable. Hence move message loglevel from pr_info to pr_debug to
resolve this issue.

CRs-Fixed: 499244
Change-Id: Ife129604a1d877a4c8c6b7cd7a75a6af2ff03578
Signed-off-by: Mayank Rana <mrana@codeaurora.org>