net/mlx5: Convert scaled ppm values outside the s32 range for PHC frequency adjustments

Represent scaled ppm as ppb to the device when the value in scaled ppm is
not representable as a 32-bit signed integer. mlx5 devices only support a
32-bit field for the frequency adjustment value in units of either scaled
ppm or ppb.

Since mlx5 devices only support a 32-bit field for the frequency adjustment
value independent of unit used, limit the maximum frequency adjustment to
S32_MAX ppb.

Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>