usb: dwc3: host: extract dwc3_host_get_irq()

Cleanup only, no functional changes.

Change-Id: Ica030ea6dc938b95ed1383f72f426188a270c73d
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Git-commit: 6d729a55cc0fc9f9a003b61491ee5868c9df5baf
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[mrana@codeaurora.org: resolved minor merge conflict]
Signed-off-by: Mayank Rana <mrana@codeaurora.org>