PCI: rcar: Remove IRQ mappings in rcar_pcie_enable_msi() failpath

The rcar_pcie_enable_msi() creates IRQ mappings using irq_create_mapping()
before requesting the IRQs using devm_request_irq(). If devm_request_irq()
fails for some reason, rcar_pcie_enable_msi() does not remove the mapping.

Pull out the code for disposing IRQ mappings from rcar_pcie_teardown_msi()
into a separate function and call it from both rcar_pcie_teardown_msi()
and rcar_pcie_enable_msi() failpath to remove the mappings correctly.

Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Phil Edworthy <phil.edworthy@renesas.com>
Cc: Simon Horman <horms+renesas@verge.net.au>
Cc: Wolfram Sang <wsa@the-dreams.de>
Cc: linux-renesas-soc@vger.kernel.org