arm64: Allow selecting Pseudo-NMI again

Now that Pseudo-NMI are fixed, allow the use of that option again

This reverts commit 96a13f57 ("arm64:
Kconfig: Make ARM64_PSEUDO_NMI depend on BROKEN for now").

Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>