bus: mhi: core: Check for IRQ availability during registration

Current design allows a controller to register with MHI successfully
without the need to have any IRQs available for use. If no IRQs are
available, power up requests to MHI can fail after a successful
registration with MHI. Improve the design by checking for the number
of IRQs available sooner within the mhi_regsiter_controller() API as
it is required to be specified by the controller.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>