arm64: isr_wrapper: fixup out of bounds for large number of irqs

In case we enable a large number of IRQs, like when enabling LPIs using
interrupts > 8192, we hit an assembler error where the immediate value
is too large.

Copy the IRQ number into x1 to permit using a large IRQ number.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>