Make get_call_rtx_from take a const rtx_insn *

Make get_call_rtx_from take a const rtx_insn *

Only one caller (in dwarf2out.c) was preventing get_call_rtx_from
from taking an rtx_insn *.  Since that caller just passes a PATTERN,
it's a trivial change to make.

2019-09-10  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* rtl.h (get_call_rtx_from): Take a const rtx_insn * instead of an rtx.
	* rtlanal.c (get_call_rtx_from): Likewise.
	* dwarf2out.c (dwarf2out_var_location): Pass the insn rather
	than the pattern to get_call_rtx_from.
	* config/i386/i386-expand.h (ix86_notrack_prefixed_insn_p): Take
	an rtx_insn * instead of an rtx.
	* config/i386/i386-expand.c (ix86_notrack_prefixed_insn_p): Likewise.

From-SVN: r275593