ixgbe: Fix incorrect bitwise operations of PTP Rx timestamp flags

ixgbe: Fix incorrect bitwise operations of PTP Rx timestamp flags

Rx timestamp does not work on 82599 and X540 because bitwise operation
of RX_HWTSTAMP flags is incorrect and ixgbe_ptp_rx_hwtstamp() is never
called. This patch fixes it to enable Rx timestamp on 82599 and X540.

Without this fix:
ptp4l[278.730]: selected /dev/ptp8 as PTP clock
ptp4l[278.733]: port 1: INITIALIZING to LISTENING on INITIALIZE
ptp4l[278.733]: port 0: INITIALIZING to LISTENING on INITIALIZE
ptp4l[278.834]: port 1: received SYNC without timestamp
ptp4l[278.835]: port 1: new foreign master 1c3947.fffe.60f9cc-1
ptp4l[279.834]: port 1: received SYNC without timestamp
ptp4l[280.834]: port 1: received SYNC without timestamp
ptp4l[281.834]: port 1: received SYNC without timestamp
ptp4l[282.834]: port 1: received SYNC without timestamp
ptp4l[282.835]: selected best master clock 1c3947.fffe.60f9cc
ptp4l[282.835]: port 1: LISTENING to UNCALIBRATED on RS_SLAVE
ptp4l[283.834]: port 1: received SYNC without timestamp

With this fix:
ptp4l[239.154]: selected /dev/ptp8 as PTP clock
ptp4l[239.157]: port 1: INITIALIZING to LISTENING on INITIALIZE
ptp4l[239.157]: port 0: INITIALIZING to LISTENING on INITIALIZE
ptp4l[240.989]: port 1: new foreign master 1c3947.fffe.60f9cc-1
ptp4l[244.989]: selected best master clock 1c3947.fffe.60f9cc
ptp4l[244.989]: port 1: LISTENING to UNCALIBRATED on RS_SLAVE
ptp4l[246.977]: master offset -899583339542096 s0 freq      +0 path delay     16222
ptp4l[247.977]: master offset -899583339617265 s1 freq  -75169 path delay     16177
ptp4l[248.977]: master offset       -130 s2 freq  -75299 path delay     16177
ptp4l[248.977]: port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED
ptp4l[249.977]: master offset         -9 s2 freq  -75217 path delay     16177
ptp4l[250.977]: master offset         88 s2 freq  -75123 path delay     16132

Fixes: a9763f3cb54c ("ixgbe: Update PTP to support X550EM_x devices")
Signed-off-by: Yusuke Suzuki <yus-suzuki@uf.jp.nec.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>