PCI: microchip: Clean up initialisation of interrupts

PCI: microchip: Clean up initialisation of interrupts

Refactor interrupt handling in _init() function into
disable_interrupts(), init_interrupts(), clear_sec_errors() and clear
ded_errors() because current code is unwieldy and prone to bugs.

Disable interrupts as soon as possible and only enable interrupts after
address translation is setup to prevent spurious axi2pcie and pcie2axi
translation errors being reported.

Link: https://lore.kernel.org/r/20230728131401.1615724-6-daire.mcnamara@microchip.com
Signed-off-by: Daire McNamara <daire.mcnamara@microchip.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>