x86/hyperv: Fix the build in the !CONFIG_KEXEC_CORE case
x86/hyperv: Fix the build in the !CONFIG_KEXEC_CORE case

Recent changes in the Hyper-V driver:

  b4370df2b1f5 ("Drivers: hv: vmbus: add special crash handler")

broke the build when CONFIG_KEXEC_CORE is not set:

  arch/x86/built-in.o: In function `hv_machine_crash_shutdown':
  arch/x86/kernel/cpu/mshyperv.c:112: undefined reference to `native_machine_crash_shutdown'

Decorate all kexec related code with #ifdef CONFIG_KEXEC_CORE.

Reported-by: Jim Davis <2c206a2580fbbd807f33aa755406225080803cdf@gmail.com>
Reported-by: Stephen Hemminger <06fa905d7f2aaced6dc72e9511c71a2a51e8aead@networkplumber.org>
Signed-off-by: Vitaly Kuznetsov <282517a3cdaae14e79e6d52f012bddb9ec2b7f0e@redhat.com>
Signed-off-by: Thomas Gleixner <00e4cf8f46a57000a44449bf9dd8cbbcc209fd2a@linutronix.de>
Cc: 21a6cafaf0e9b0080692d699c1538d0dfa42b47a@linuxdriverproject.org
Cc: K. Y. Srinivasan <bcbf172338421f26297a2592698edf8cc84ecbef@microsoft.com>
Cc: Haiyang Zhang <6c26c5044f1d67d9ed5db6596adb36d25510e216@microsoft.com>
Cc: Greg Kroah-Hartman <4645f7897fd33786a2ee1264d590b3c400559d85@linuxfoundation.org>
Cc: Peter Zijlstra <3fddac958924aef220f202ca567388ddab3f14a8@infradead.org>
Cc: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>
Link: http://lkml.kernel.org/r/1443002577-25370-1-git-send-email-282517a3cdaae14e79e6d52f012bddb9ec2b7f0e@redhat.com
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs