opcodes cgen: remove use of PTR

Note that opcodes is regenerated with cgen commit d1dd5fcc38e reverted,
due to failure of bpf to compile with that patch applied.

.../opcodes/bpf-opc.c:57:11: error: conversion from ‘long unsigned int’ to ‘unsigned int’ changes value from ‘18446744073709486335’ to ‘4294902015’ [-Werror=overflow]
   57 |   64, 64, 0xffffffffffff00ff, { { F (F_IMM32) }, { F (F_OFFSET16) }, { F (F_SRCLE) }, { F (F_OP_CODE) }, { F (F_DSTLE) }, { F (F_OP_SRC) }, { F (F_OP_CLASS) }, { 0 } }
plus other similar errors.

cpu/
	* mep.opc (print_tpreg, print_spreg): Delete unnecessary
	forward declarations.  Replace PTR with void *.
	* mt.opc (print_dollarhex, print_pcrel): Delete forward decls.
opcodes/
	* bpf-desc.c, * bpf-dis.c, * cris-desc.c,
	* epiphany-desc.c, * epiphany-dis.c,
	* fr30-desc.c, * fr30-dis.c, * frv-desc.c, * frv-dis.c,
	* ip2k-desc.c, * ip2k-dis.c, * iq2000-desc.c, * iq2000-dis.c,
	* lm32-desc.c, * lm32-dis.c, * m32c-desc.c, * m32c-dis.c,
	* m32r-desc.c, * m32r-dis.c, * mep-desc.c, * mep-dis.c,
	* mt-desc.c, * mt-dis.c, * or1k-desc.c, * or1k-dis.c,
	* xc16x-desc.c, * xc16x-dis.c,
	* xstormy16-desc.c, * xstormy16-dis.c: Regenerate.