x86/asm: Drop __GET_CURRENT()

x86/asm: Drop __GET_CURRENT()

__GET_CURRENT() is dangerous to use, as is easy to confuse with GET_CURRENT(),
but strictly depends on the regster parameter already having the STACK_END
value in it.  Also, there is no reason to special case accesses of
current_vcpu differently to other cpuinfo fields.

Expand __GET_CURRENT() in its current users, and remove the macro.

Take the opportunity to replace the GET_CURRENT() in the cstar path which
doesn't need to recalculate STACK_END.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>