Merge remote-tracking branch 'remotes/xtensa/tags/20181001-xtensa' into staging

Merge remote-tracking branch 'remotes/xtensa/tags/20181001-xtensa' into staging

target/xtensa: preparation for FLIX support

Separate generation of per-instruction code (such as raising exceptions
and terminating TB) from per-opcode code.

# gpg: Signature made Mon 01 Oct 2018 19:14:34 BST
# gpg:                using RSA key 51F9CC91F83FA044
# gpg: Good signature from "Max Filippov <filippov@cadence.com>"
# gpg:                 aka "Max Filippov <max.filippov@cogentembedded.com>"
# gpg:                 aka "Max Filippov <jcmvbkbc@gmail.com>"
# Primary key fingerprint: 2B67 854B 98E5 327D CDEB  17D8 51F9 CC91 F83F A044

* remotes/xtensa/tags/20181001-xtensa:
  target/xtensa: extract gen_check_interrupts call
  target/xtensa: make rsr/wsr helpers return void
  target/xtensa: extract unconditional TB termination via slot 0
  target/xtensa: always end TB on CCOUNT access/CCOMPARE write
  target/xtensa: change SR number checks to assertions
  target/xtensa: extract unconditional TB termination
  target/xtensa: extract test for division by zero
  target/xtensa: extract test for cpdisabled exception
  target/xtensa: extract test for alloca exception
  target/xtensa: extract test for window underflow exception
  target/xtensa: extract test for window overflow exception
  target/xtensa: extract test for debug exception
  target/xtensa: extract test for syscall instruction
  target/xtensa: extract test for privileged instruction
  target/xtensa: extract test for an illegal instruction

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>