objtool: Make stack validation frame-pointer-specific

Now that CONFIG_STACK_VALIDATION is frame-pointer specific, do the same
for the '--stackval' option.  Now the '--no-fp' option is redundant and
can be removed.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/f563fa064b3b63d528de250c72012d49e14742a3.1650300597.git.jpoimboe@redhat.com