fix some issues in x32 syscall_cp_fixup

- the nanosleep fixup "fixed" the second timespec* argument erroneusly.
- the futex fixup was missing the check for FUTEX_WAIT.
- general cleanup using a macro.
fix x32 syscall arch.h timespec fixup code

it's legal to call the __syscall functions with more arguments than
necessary, and the __syscall_cp cancel dummy impl. does just that.

thus we must insert the switch for all possible syscalls numbers
into all of the syscallN inline functions.