usb: gadget: Ignore the second set_config from the host

Some USB hosts may send SET_CONFIGURATION with same value twice.
The current code implementation of android_work() issues disconnect
event to userspace if SetConfiguration with non-zero value is sent
twice. The Userspace application may disconnect USB and it causes
fail to connect to the USB host.

Fix this by ignoring the second time SET_CONFIGURATION request
from the host only for the same configuration value twice.

CRs-Fixed: 661220
Change-Id: Iec8dd7824fa9f371ea147784cf9137aa88a7128e
Signed-off-by: ChandanaKishori Chiluveru <cchilu@codeaurora.org>