usb: ehci-msm-hsic: use work_queue to invoke runtime_pm_allow

runtime_pm_allow() uses spin_lock_irq and spin_unlock_irq
which unconditionally enables irq irrespective of irq status.
Hence, this API shouldn't be called from interrupt context.
Use work_queue in driver to invoke runtime_pm_allow() instead
of isr.

Change-Id: If9f483573ffd188effcfc3871edaf205aa889e22
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>