fix !CONFIG_FRAME_POINTER, !CONFIG_UTRACE case

fix !CONFIG_FRAME_POINTER, !CONFIG_UTRACE case

In a kernel without FRAME_POINTERS (using the DWARF UNWINDER) and without
UTRACE I see the following in latest git master:
[...]
In file included from /tmp/stap/share/systemtap/runtime/stack.c:56:0,
                 from /tmp/stapPHqTen/stap_12068.c:52:
/tmp/stap/share/systemtap/runtime/stack-i386.c: In function "__stp_stack_print":
/tmp/stap/share/systemtap/runtime/stack-i386.c:69:25: error: implicit declaration of function "uprobe_get_pc".

AFAICT the autoconf test should result in STAPCONF_UPROBE_GET_PC=0 for the
case where CONFIG_UTRACE is unset since UPROBES requires UTRACE.

Signed-off-by: Tony Jones <tonyj@suse.de>