When compiling C, a ?: between two values of the same SVE type
currently gives an error such as:
incompatible operand types ('svint8_t' (aka '__SVInt8_t') and 'svint8_t')
It's supposed to be valid to select between (cv-qualified versions of)
the same SVE type, so this patch adds that case.
These expressions already work for C++ and are tested by