KVM: x86: Move MMIO write tracing into vcpu_mmio_write()

KVM: x86: Move MMIO write tracing into vcpu_mmio_write()

Move the invocation of MMIO write tracepoint into vcpu_mmio_write() and
drop its largely-useless wrapper to cull pointless code and to make the
code symmetrical with respect to vcpu_mmio_read().

No functional change intended.

Tested-by: Tom Lendacky <thomas.lendacky@gmail.com>
Tested-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Link: https://patch.msgid.link/20260225012049.920665-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>