Merge remote-tracking branch 'remotes/rth-gitlab/tags/pull-tcg-20210730' into staging

Fix double bswap in 16-byte atomic store
Mark nios2 raise_exception noreturn

# gpg: Signature made Fri 30 Jul 2021 19:24:44 BST
# 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-gitlab/tags/pull-tcg-20210730:
  target/nios2: Mark raise_exception() as noreturn
  accel/tcg: Remove double bswap for helper_atomic_sto_*_mmu

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