arm64: mm: Handle PAN faults on uaccess CPY* instructions

A subsequent patch will use CPY* instructions to copy between user and
kernel memory. Add handling for PAN faults caused by an intended kernel
memory access erroneously accessing user memory, in order to make it
easier to debug kernel bugs and to keep the same behavior as with
regular loads/stores.

Signed-off-by: Kristina Martšenko <kristina.martsenko@arm.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20250228170006.390100-3-kristina.martsenko@arm.com


[catalin.marinas@arm.com: Folded the extable search into insn_may_access_user()]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>