arm64: entry: remove test_irqs_unmasked macro

We haven't needed the test_irqs_unmasked macro since commit:

  105fc3352077bba5 ("arm64: entry: move el1 irq/nmi logic to C")

... and as we convert more of the entry logic to C it is decreasingly
likely we'll need it in future, so let's remove the unused macro.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Acked-by: Marc Zyngier <maz@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210323181201.18889-1-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>