x86/defconfig: Enable CONFIG_LOCALVERSION_AUTO=y in the defconfig

With CONFIG_LOCALVERSION_AUTO=y enabled, 'uname' provides
much more useful output on debug kernels:

 Before:

   # CONFIG_LOCALVERSION_AUTO is not set

   $ uname -a
   Linux localhost 5.16.0-rc7+ #4563 SMP PREEMPT Thu Dec 30 08:28:38 CET 2021 x86_64 GNU/Linux

 After:

   # CONFIG_LOCALVERSION_AUTO=y

   $ uname -a
   Linux localhost 5.16.0-rc7-02294-g5537f9709b16 #4562 SMP PREEMPT Thu Dec 30 08:27:17 CET 2021 x86_64 GNU/Linux

This is particularly valuable during bisection, if we want to double check
the exact kernel version we are testing.

(Just remove the config line, the global Kconfig default for this is default-y.)

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>