gdb/testsuite: Move helper function into lib/dwarf.exp

gdb/testsuite: Move helper function into lib/dwarf.exp

Every time I write a test making use of the DWARF assembler I end up
copying in the function get_func_info.  Duplicating code is bad, so
lets put this function into lib/dwarf.exp and remove all of the
duplicates.

There should be no changes in the testsuite behaviour after this
commit.

gdb/testsuite/ChangeLog:

	* gdb.dwarf2/dw2-inline-many-frames.exp (get_func_info): Delete.
	* gdb.dwarf2/dw2-inline-small-func.exp: Pass options to
	get_func_info.
	(get_func_info): Delete.
	* gdb.dwarf2/dw2-is-stmt-2.exp (get_func_info): Delete.
	* gdb.dwarf2/dw2-is-stmt.exp (get_func_info): Delete.
	* lib/dwarf.exp (get_func_info): New function.