arm64: Save esr in pt_regs

arm64: Save esr in pt_regs

To avoid passing around an extra register everywhere, save esr in
pt_regs like the rest. For proper alignment we need to have a second
(unused) register. All the printfs have to be adjusted, since
it's now an unsigned long and not an int.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>