[gdb/testsuite] Drop src arg of MACRO_AT_{func,range}

[gdb/testsuite] Drop src arg of MACRO_AT_{func,range}

The dwarf assembly procs MACRO_AT_func and MACRO_AT_range have a src
parameter, which is set to $srcdir/$subdir/$srcfile in every single call.

Drop the src parameter and hardcode usage of $srcdir/$subdir/$srcfile in the
procs.

Build and reg-tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2020-07-17  Tom de Vries  <tdevries@suse.de>

	* lib/dwarf.exp (Dwarf::MACRO_AT_func, Dwarf::MACRO_AT_range): Drop
	src parameter.
	* gdb.dlang/watch-loc.exp: Update MACRO_AT_{func,range} calls.
	* gdb.dwarf2/bitfield-parent-optimized-out.exp: Same.
	* gdb.dwarf2/dw2-ifort-parameter.exp: Same.
	* gdb.dwarf2/dw2-opt-structptr.exp: Same.
	* gdb.dwarf2/dwz.exp: Same.
	* gdb.dwarf2/implptr-optimized-out.exp: Same.
	* gdb.dwarf2/implref-array.exp: Same.
	* gdb.dwarf2/implref-const.exp: Same.
	* gdb.dwarf2/implref-global.exp: Same.
	* gdb.dwarf2/implref-struct.exp: Same.
	* gdb.dwarf2/info-locals-optimized-out.exp: Same.
	* gdb.dwarf2/opaque-type-lookup.exp: Same.
	* gdb.dwarf2/var-access.exp: Same.
	* gdb.dwarf2/varval.exp: Same.
	* gdb.trace/entry-values.exp: Same.