aarch64: implement system call assembly instruction svc

[wkozaczuk]

This would be equivalent to what we do on x86_64 to implement the SYSCALL instruction handler. The equivalent on ARM is SVC. There is a good article describing how system call handling is implemented in Linux - https://eastrivervillage.com/Anatomy-of-Linux-system-call-in-ARM64/index.html.
Please note we would also want to implement a dedicated syscall stack to properly support Golang executables.

[wkozaczuk]

The golang-pie-example crashes like so:

OSv v0.55.0-292-g6dec325e
eth0: 192.168.122.15
Booted up in 90.43 ms
Cmdline: /hello.so
unexpected synchronous exception, EC: 0x0015
[registers]
PC: 0x00001000000cd7e4 <???+841700>
X00: 0x0000000000000000 X01: 0x0000000000002000 X02: 0x00002000006feee8
X03: 0x0000000000002350 X04: 0xffffa000412e3e30 X05: 0x0000000010000000
X06: 0x0000000000000000 X07: 0x0000000000000003 X08: 0x000000000000007b
X09: 0x000000000d35ec75 X10: 0x0000000000000006 X11: 0x000000006e43a319
X12: 0x000000006e43a319 X13: 0x000000006e43a319 X14: 0x0000000000000000
X15: 0x0000000000000000 X16: 0x0000200000700ee8 X17: 0x00000000402d3eb4
X18: 0x0000000000000000 X19: 0xffffa000412e3810 X20: 0x0000200000700a48
X21: 0x00000000406f8000 X22: 0x0000000000000001 X23: 0xffffa000412e3810
X24: 0xffffa000412e3800 X25: 0x0000200000100d50 X26: 0x00002000007009a0
X27: 0x0000200000700ec0 X28: 0x00001000001be3a0 X29: 0x00002000006feeb8
X30: 0x0000100000099adc SP:  0x00002000006feec0 ESR: 0x0000000056000000
PSTATE: 0x0000000020000345
Aborted

[backtrace]
0x000000004020b8d0 <???+1075886288>
0x000010000009a23c <???+631356>
0xa9bf67f8a9bf6ff6 <???+-1447071754>