Since AVX10.1/256 will also allow 64 bit mask register, we will
remove the restriction for size of the mask register in AVX10.
gas/ChangeLog:
* config/tc-i386.c (VSZ128, VSZ256, VSZ512): New.
(VEX_check_encoding): Remove opcode_modifier check for vsz.
* testsuite/gas/i386/avx10-vsz.l: Remove testcases for mask
registers since they are not needed.
* testsuite/gas/i386/avx10-vsz.s: Ditto.