mlxsw: Rename 'read_frc_capable' bit to 'read_clock_capable'

Rename the 'read_frc_capable' bit to 'read_clock_capable' since now it can
be both the FRC and UTC clocks.

Signed-off-by: Danielle Ratson <danieller@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>