kvm: remove one useless check extension

We already check KVM_CAP_IRQFD in generic once enable CONFIG_HAVE_KVM_IRQFD,

kvm_vm_ioctl_check_extension_generic()
    |
    + switch (arg) {
    +   ...
    +   #ifdef CONFIG_HAVE_KVM_IRQFD
    +       case KVM_CAP_IRQFD:
    +   #endif
    +   ...
    +   return 1;
    +   ...
    + }
    |
    + kvm_vm_ioctl_check_extension()

So its not necessary to check this in arch again, and also fix one typo,
s/emlation/emulation.
Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

arch/arm/kvm/arm.c

@@ -171,7 +171,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	int r;
 	switch (ext) {
 	case KVM_CAP_IRQCHIP:
-	case KVM_CAP_IRQFD:
 	case KVM_CAP_IOEVENTFD:
 	case KVM_CAP_DEVICE_CTRL:
 	case KVM_CAP_USER_MEMORY:

include/uapi/linux/kvm.h

@@ -895,7 +895,7 @@ struct kvm_xen_hvm_config {
  *
  * KVM_IRQFD_FLAG_RESAMPLE indicates resamplefd is valid and specifies
  * the irqfd to operate in resampling mode for level triggered interrupt
- * emlation.  See Documentation/virtual/kvm/api.txt.
+ * emulation.  See Documentation/virtual/kvm/api.txt.
  */
 #define KVM_IRQFD_FLAG_RESAMPLE (1 << 1)