The recent move of hv_do_rep_hypercall() to this file adds
a reference to touch_nmi_watchdog(). Its function definition
is included indirectly when compiled on x86, but not when
compiled on ARM64. So add the explicit #include.

No functional change.
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/1626058204-2106-1-git-send-email-mikelley@microsoft.comSigned-off-by: Wei Liu <wei.liu@kernel.org>