x86/PMU: make {acquire,release}_pmu_ownership names consistent

x86/PMU: make {acquire,release}_pmu_ownership names consistent

The function names were inconsistent with acquire and release being
called acquire_pmu_ownership() and release_pmu_ownship() respectively.
Function prototypes were available for both spellings so this change
makes them consistent and drops the dual function prototypes.
Additionally change the internal variable names within those functions
to ownership as well.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>