arm64: convert syscall trace logic to C

arm64: convert syscall trace logic to C

Currently syscall tracing is a tricky assembly state machine, which can
be rather difficult to follow, and even harder to modify. Before we
start fiddling with it for pt_regs syscalls, let's convert it to C.

This is not intended to have any functional change.

Signed-off-by: Mark Rutland <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Will Deacon <[email protected]>