usb: bdc: Add support for suspend/resume

Based on a previous commit by Danesh Petigara <dpetigara@broadcom.com>
that added resume to solve the following problem:
"The BDC driver will fail after resuming from S3 suspend and this
will cause any upper layer gadget driver to fail."
This commit also adds support for suspend and manages the clock during
suspend/resume.

Signed-off-by: Al Cooper <alcooperx@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>