hw-breakpoints, x86: Fix modular KVM build

This build error:

arch/x86/kvm/x86.c:3655: error: implicit declaration of function 'hw_breakpoint_restore'

Happens because in the CONFIG_KVM=m case there's no 'CONFIG_KVM' define
in the kernel - it's CONFIG_KVM_MODULE in that case.

Make the prototype available unconditionally.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
LKML-Reference: <1258114575-32655-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>