s390: extend expoline to BC instructions

s390: extend expoline to BC instructions

BugLink: http://bugs.launchpad.net/bugs/1783418
[ Upstream commit 6deaa3bbca804b2a3627fd685f75de64da7be535 ]

The BPF JIT uses a 'b <disp>(%r<x>)' instruction in the definition
of the sk_load_word and sk_load_half functions.

Add support for branch-on-condition instructions contained in the
thunk code of an expoline.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>