Merge remote-tracking branch 'remotes/riscv/tags/riscv-qemu-2.13-minor-fixes-3' into...

RISC-V: QEMU 2.13 Minor Fixes

* Require libfdt when configuring for 'riscv*-softmmu'
* Increase HTIF priority and allow zero base address

# gpg: Signature made Wed 09 May 2018 11:15:33 BST
# gpg:                using DSA key 6BF1D7B357EF3E4F
# gpg: Good signature from "Michael Clark <michaeljclark@mac.com>"
# gpg:                 aka "Michael Clark <mjc@sifive.com>"
# gpg:                 aka "Michael Clark <michael@metaparadigm.com>"
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 7C99 930E B17C D8BA 073D  5EFA 6BF1 D7B3 57EF 3E4F

* remotes/riscv/tags/riscv-qemu-2.13-minor-fixes-3:
  riscv: requires libfdt
  riscv: htif: increase the priority of the htif subregion
  riscv: spike: allow base == 0

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