x86/vmx: Improvements to vmx_{dis,en}able_intercept_for_msr()

x86/vmx: Improvements to vmx_{dis,en}able_intercept_for_msr()

 * Shorten the names to vmx_{clear,set}_msr_intercept()
 * Use an enumeration for MSR_TYPE rather than a plain integer
 * Introduce VMX_MSR_RW, as most callers alter both the read and write
   intercept at the same time.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>