Drop the DRM IRQ midlayer in favor of Linux IRQ interfaces. DRM's
IRQ helpers are mostly useful for UMS drivers. Modern KMS drivers
don't benefit from using it.

DRM IRQ callbacks are now being called directly or inlined.

The interrupt number returned by pci_msi_vector() is now stored
in struct amdgpu_irq. Calls to pci_msi_vector() can fail and return
a negative errno code. Abort initlaizaton in thi case. The DRM IRQ
midlayer does not handle this correctly.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210803090704.32152-2-tzimmermann@suse.de