net/mlx5e: Use hard-coded 4K page size for RQ/SQ/CQ

The page size of the device's RQ/SQ/CQ objects is defined in 4K
units regardless of the system pages size.
Thus using the Linux's PAGE_SHIFT macro yields wrong device
configuration in systems where PAGE_SHIFT!=12.

Signed-off-by: Achiad Shochat <achiad@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>