alpha: add Linux syscall table numbers

Crikey, Alpha's syscall table is a right mess. Anyway, with enough sed
and perl-fu, here's something that looks about right for trinity. I had
to hand-hack the result to remove a whole bunch of obsolete syscalls
that trinity doesn't care about.

I also fixed up some missing Alpha ptrace requests with dummy values.

Signed-off-by: Will Deacon <will.deacon@arm.com>