cgen: remove use of PTR

cgen: remove use of PTR

Nowadays binutils and sim both require at least C99 compilers,
negating the need for macros like PTR.

	* desc-cpu.scm (gen-maybe-multi-ifld): Remove PTR casts.
	(gen-multi-ifield-nodes, gen-operand-table): Likewise.
	* desc.scm (gen-table-entry): Likewise.
	* opc-itab.scm (gen-minsn-table-entry): Likewise.
	(gen-minsn-opcode-entry): Likewise.
	* opc-asmdis.scm (gen-print-switch): Emit void * in place of PTR.