x86/platform/intel-mid: Make IRQ allocation a bit more flexible

In the future we would use dynamic allocation for IRQ which brings
non-1:1 mapping for IOAPIC domain. Thus, we need to respect return value
of mp_map_gsi_to_irq() and assign it back to the device structure.

Besides that we need to read GSI from interrupt pin register to avoid
cases when some drivers will try to initialize PCI device twice in a row
which will call pcibios_enable_irq() twice as well.

	serial 0000:00:04.1: Mapped GSI28 to IRQ5
	serial 0000:00:04.2: Mapped GSI29 to IRQ5
	serial 0000:00:04.3: Mapped GSI54 to IRQ5
	8250_mid 0000:00:04.1: Mapped GSI28 to IRQ5
	8250_mid 0000:00:04.2: Mapped GSI29 to IRQ6
	8250_mid 0000:00:04.3: Mapped GSI54 to IRQ7

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-pci@vger.kernel.org
Link: http://lkml.kernel.org/r/20170724173402.12939-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>