Merge tag 'pull-semi-20220914' of https://gitlab.com/rth7680/qemu into staging

Convert m68k to semihosting/syscalls.h.
Convert nios2 to semihosting/syscalls.h.
Allow optional use of semihosting from userspace.

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* tag 'pull-semi-20220914' of https://gitlab.com/rth7680/qemu

:
  target/riscv: Honour -semihosting-config userspace=on and enable=on
  target/xtensa: Honour -semihosting-config userspace=on
  target/nios2: Honour -semihosting-config userspace=on
  target/mips: Honour -semihosting-config userspace=on
  target/m68k: Honour -semihosting-config userspace=on
  target/arm: Honour -semihosting-config userspace=on
  semihosting: Allow optional use of semihosting from userspace
  target/m68k: Convert semihosting errno to gdb remote errno
  target/m68k: Use semihosting/syscalls.h
  target/nios2: Convert semihosting errno to gdb remote errno
  target/nios2: Use semihosting/syscalls.h

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>