RISC-V: PR28291, Fix the gdb fails that PR27916 caused.

RISC-V: PR28291, Fix the gdb fails that PR27916 caused.

* According to PR28291, we get the following unexpected gdb behavior,

(gdb) disassemble 0x0,+4
Dump of assembler code from 0x0 to 0x4:
   0x0000000000000000:
   0x0000000000000001:
   0x0000000000000002:
   0x0000000000000003:
End of assembler dump.

* This patch should fix it to the right behavior,

(gdb) disassemble 0x0,+4
Dump of assembler code from 0x0 to 0x4:
   0x0000000000000000:  Cannot access memory at address 0x0

opcodes/
    pr 28291
    * riscv-dis.c (print_insn_riscv): Return STATUS if it is not zero.