Add support for 8-bit and 24-bit shifts in the z80 assembler.

	PR 27415
	* config/tc-z80.c (emit_data_val): Add support for 8-bit and
	24-bit shifts.
	* testsuite/gas/z80/z80_reloc.a: Update tests.
	* testsuite/gas/z80/z80_reloc.d: Update expected disassembly.