x86/vpmu: rename {svm,vmx}_vpmu_initialise to {amd,core2}_vpmu_initialise

x86/vpmu: rename {svm,vmx}_vpmu_initialise to {amd,core2}_vpmu_initialise

PMU virtualization is not dependent on the hardware virtualization support.
Rename {svm,vmx}_vpmu_initialise to {amd,core2}_vpmu_initialise because
the {svm,vmx} prefix is misleading.

Take the opportunity to remove the also misleading comment stating that
vpmu is specific to hvm guests, and correct the filename.

No functional change intended.

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>