net/bnxt: avoid hard coded values when reading counters

net/bnxt: avoid hard coded values when reading counters

Instead of using hardcoded values for the byte/pkt value shifts/masks
to read from the HW counters, use the shift/mask values from the device
template params

Reviewed-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>
Signed-off-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>