Merge remote-tracking branch 'remotes/rth/tags/pull-sfp-20191030' into staging

Use hardfloat for float32_to_float64

# gpg: Signature made Wed 30 Oct 2019 18:06:19 GMT
# gpg:                using RSA key 7A481E78868B4DB6A85A05C064DF38E8AF7E215F
# gpg:                issuer "richard.henderson@linaro.org"
# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>" [full]
# Primary key fingerprint: 7A48 1E78 868B 4DB6 A85A  05C0 64DF 38E8 AF7E 215F

* remotes/rth/tags/pull-sfp-20191030:
  softfp: Added hardfloat conversion from float32 to float64

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