target/xtensa updates for v8.0:

- enable testing big-endian xtensa cores

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# gpg: Signature made Thu 16 Mar 2023 20:10:16 GMT
# gpg:                using RSA key 2B67854B98E5327DCDEB17D851F9CC91F83FA044
# gpg:                issuer "jcmvbkbc@gmail.com"
# gpg: Good signature from "Max Filippov <filippov@cadence.com>" [unknown]
# gpg:                 aka "Max Filippov <max.filippov@cogentembedded.com>" [full]
# gpg:                 aka "Max Filippov <jcmvbkbc@gmail.com>" [full]
# Primary key fingerprint: 2B67 854B 98E5 327D CDEB  17D8 51F9 CC91 F83F A044

* tag '20230316-xtensa' of https://github.com/OSLL/qemu-xtensa

:
  tests/tcg/xtensa: allow testing big-endian cores
  tests/tcg/xtensa: add linker.ld to CLEANFILES

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