aarch64: Fix sibcalls involving shared-ZT0 functions

aarch64: Fix sibcalls involving shared-ZT0 functions

In:

  void bar() __arm_inout("za");
  void foo() __arm_inout("za", "zt0") { bar(); }

foo cannot tail-call bar because foo needs to restore ZT0 after
the call.  I'd forgotten to update the ok_for_sibcall rules
to handle this when adding SME2.

Thanks to Sander de Smalen for the spot.

gcc/
	* config/aarch64/aarch64.cc (aarch64_function_ok_for_sibcall):
	Check that each individual piece of state is shared in the same
	way, rather than using an aggregate check for PSTATE.ZA.

gcc/testsuite/
	* gcc.target/aarch64/sme/sibcall_9.c: New test.