Merge remote-tracking branch 'remotes/xtensa/tags/20170317-xtensa' into staging

target/xtensa fixes for 2.9:

- fix build failure when FDT support is not enabled;
- correctly pass command line arguments to semihosting guests.

# gpg: Signature made Fri 17 Mar 2017 18:14:01 GMT
# gpg:                using RSA key 0x51F9CC91F83FA044
# 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/20170317-xtensa:
  target/xtensa: fix semihosting argc/argv implementation
  target/xtensa: xtfpga: load DTB only when FDT support is enabled

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