s390: Make operand table indices relative to each other

s390: Make operand table indices relative to each other

This is a purely mechanical change. It allows subsequent insertions into
the operands table without having to renumber all operand indices.

The only differences in the resulting ELF object are in the .debug_info
section. This has been confirmed by diffing the following xxd and readelf
output:

xxd s390-opc.o
readelf -aW -x .text -x .data -x .bss -x .rodata -x .debug_info \
  -x .symtab -x .strtab -x .shstrtab --debug-dump s390-opc.o

opcodes/
	* s390-opc.c: Make operand table indices relative to each other.

Signed-off-by: Jens Remus <jremus@linux.ibm.com>
Reviewed-by: Andreas Krebbel <krebbel@linux.ibm.com>