Commit bbacc0c1 (KVM: Rename KVM_MEMORY_SLOTS -> KVM_USER_MEM_SLOTS)
broke KVM/ARM by changing a global #define.

Apply the same change to fix the compilation breakage.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NGleb Natapov <gleb@redhat.com>