tune-thunderx: Set the correct PACKAGE_EXTRA_ARCHS_tune-thunderx

tune-thunderx: Set the correct PACKAGE_EXTRA_ARCHS_tune-thunderx

The value of PACKAGE_EXTRA_ARCHS_tune-thunderx should be based on
PACKAGE_EXTRA_ARCHS_tune-armv8a-crc-crypto instead of armv8a-crc-crypto.
Otherwise we would get some sanity check error like this:
    OE-core's config sanity checker detected a potential misconfiguration.
    Either fix the cause of this error or at your own risk disable the checker (see sanity.conf).
    Following is the list of potential problems / advisories:

    Error, the PACKAGE_ARCHS variable (all any noarch armv8a-crc-crypto thunderx qemuarm64) for DEFAULTTUNE (thunderx) does not contain TUNE_PKGARCH (aarch64)

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>