x86/unwinder: Make CONFIG_UNWINDER_ORC=y the default in the 64-bit defconfig

Increase testing coverage by turning on the primary x86 unwinder for
the 64-bit defconfig.

Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/configs/x86_64_defconfig

@@ -299,6 +299,7 @@ CONFIG_DEBUG_STACKOVERFLOW=y
 # CONFIG_DEBUG_RODATA_TEST is not set
 CONFIG_DEBUG_BOOT_PARAMS=y
 CONFIG_OPTIMIZE_INLINING=y
+CONFIG_ORC_UNWINDER=y
 CONFIG_SECURITY=y
 CONFIG_SECURITY_NETWORK=y
 CONFIG_SECURITY_SELINUX=y