Revert "opcodes: microblaze: Add new bit-field instructions"

This reverts commit 6bbf2495.

Maciej W. Rozycki <macro@orcam.me.uk>:
 Yet it has caused numerous regressions:

microblaze-elf  +FAIL: unordered .debug_info references to .debug_ranges
microblaze-elf  +FAIL: binutils-all/pr26548
microblaze-elf  +FAIL: readelf -Wwi pr26548e (reason: unexpected output)
microblaze-elf  +FAIL: readelf --debug-dump=loc locview-1 (reason: unexpected output) Yet it has caused numerous regressions:
microblaze-elf  +FAIL: unordered .debug_info references to .debug_ranges
microblaze-elf  +FAIL: binutils-all/pr26548
microblaze-elf  +FAIL: readelf -Wwi pr26548e (reason: unexpected output)
...