In the encoding groups
* floating-point data-processing (1 source)
* floating-point data-processing (2 source)
* floating-point data-processing (3 source)
* floating-point immediate
* floating-point compare
* floating-ponit conditional compare
* floating-point conditional select
bit 31 is M and bit 29 is S (and bit 30 is 0, already checked at
this point in the decode). None of these groups allocate any
encoding for M=1 or S=1. We checked this in disas_fp_compare(),
disas_fp_ccomp() and disas_fp_csel(), but missed it in disas_fp_1src(),
disas_fp_2src(), disas_fp_3src() and disas_fp_imm().
We also missed that in the fp immediate encoding the imm5 field
must be all zeroes.
Correctly UNDEF the unallocated encodings here.
Backports commit c1e20801f5ee53472dbf2757df605543f3f4ce0b from qemu
f7d78d9e08