[gdb/testsuite] Fix require dwarf2_support check in some test-cases

[gdb/testsuite] Fix require dwarf2_support check in some test-cases

On x86_64-freebsd, I ran into trouble with test-case
gdb.dwarf2/macro-source-path-clang14-dw4.exp (and similar), and I managed to
reproduce the problem on x86_64-linux by making dwarf2_support return 0.

The failure looks like:
...
UNSUPPORTED: $exp: require failed: dwarf2_support
UNRESOLVED: $exp: testcase aborted due to invalid command name: do_test
ERROR: tcl error sourcing $exp.
...

I fixed a similar problem in commit 3e488d8ccd0 ("[gdb/testsuite] Fix
gdb.dwarf2/dw-form-strx-out-of-bounds.exp with make-check-all.sh").

Fix this by moving "require dwarf2_support" from
gdb.dwarf2/macro-source-path.exp.tcl to the files including it.

Tested on x86_64-linux.