K 10
svn:author
V 3
kib
K 8
svn:date
V 27
2017-09-28T08:46:15.260388Z
K 7
svn:log
V 541
Restore a part of r323722.

Do not return from interrupt using the POP_FRAME;iret instruction
sequence, always jump to doreti.

The user segments selectors saved on the stack might become invalid
because userspace manipulated LDT in a parallel thread.  trap() is
aware of such issue, but it is only prepared to handle it at iret and
segment registers load operations in doreti path.

Also remove POP_FRAME macro because it is no longer used.

Reviewed by:	bde, jhb (as part of r323722)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

END