riscv_disasm.c: Fix out-of-bounds reads

riscv_disasm.c: Fix out-of-bounds reads

The riscv_disasm function reads instruction mnemonics from static
arrays based on the Control and Status Register (CSR) number encoded
in an instruction.  Two separate bounds checks performed before reading
from these arrays had incorrect upper bounds and allowed out-of-bounds
reads.

Fix two CSR bounds checks to prevent this. The affected CSR numbers that
are no longer included in the modified checks are now properly handled
in a generic CSR handler in the riscv_disasm function.

Signed-off-by: Aaron Merey <amerey@redhat.com>