usb: bam: Skip IPA initialization if not enabled

Calling into IPA APIs when it is not enabled in the HW may
lead to unexpected results. Use the function ipa_is_ready()
to determine if IPA RM resources need to be created.

Change-Id: Id0214ba155e67bf000fbc8f2b928db1022aa9287
Signed-off-by: Jack Pham <jackp@codeaurora.org>