qemu: Upgrade 5.0.0 -> 5.1.0

qemu: Upgrade 5.0.0 -> 5.1.0

* Drop backported CVE fixes
* Drop cpu backtrace patch from 2015 for debugging an issue which we no longer see
  (patch throws rejects, files have moved)
* Update mips patch to account for file renames
* Update chardev patch to match upstream code changes
* Update webkitgtk patch, qemumips build works ok but qemux86 musl webkitgtk still
  fails. Need to figure out the correct fix and upstream it for this, current
  revert patch is not maintainable.

Release notes for 5.1.0 mention slight qemumips performance improvements
which would be valuable to us. My tests show no improvement in qemumips
testimage execution time for core-image-sato-sdk.

Fix a ptest issue for a file looking for /usr/bin/bash when we have
/bin/bash.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>