drivers/perf: arm_pmu: handle no platform_device

drivers/perf: arm_pmu: handle no platform_device

BugLink: https://bugs.launchpad.net/bugs/1689661
In armpmu_dispatch_irq() we look at arm_pmu::plat_device to acquire
platdata, so that we can defer to platform-specific IRQ handling,
required on some 32-bit parts. With the advent of ACPI we won't always
have a platform_device, and so we must avoid trying to dereference
fields from it.

This patch fixes up armpmu_dispatch_irq() to avoid doing so, introducing
a new armpmu_get_platdata() helper.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from commit 7654137071fa706e5c91f4f27bc2a5cd7e435a9b)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>