Incorrect code generation with PULP march with 20231017 release

[pascalgouedo]

When compiling Embench tests, following errors are reported:

march=rv32imc_zicsr_zifencei_xcvmem_xcvmac_xcvbi_xcvalu_xcvsimd_xcvbitmanip

• sglib-combined Assembler messages: Error: illegal operands `sb zero,a2(a5)'
• st error: unrecognizable insn: 133 | } | ^ (insn 13 12 14 4 (set (reg:DF 12 a2) (mem:DF (plus:SI (reg/v/f:SI 140 [ Array ]) (reg:SI 143)) [2 MEM[(double )Array_16(D) + _9 1]+0 S8 A64])) "embench/src/st/libst.c":131:10 -1 (nil)) during RTL pass: vregs embench/src/st/libst.c:133:1: internal compiler error: in extract_insn, at recog.cc:2791

[MaryBennett]

Fixed in PR #81