net: mvpp2: remove mvpp2_bm_cookie_{build,pool_get}

This commit removes the useless remove
mvpp2_bm_cookie_{build,pool_get} functions. All what
mvpp2_bm_cookie_build() was doing is compute a 32-bit value by
concatenating the pool number and the CPU number... only to get the pool
number re-extracted by mvpp2_bm_cookie_pool_get() later on.

Instead, just get the pool number directly from RX descriptor status,
and pass it to mvpp2_pool_refill() and mvpp2_rx_refill().

This has the added benefit of dropping a smp_processor_id() call in a
migration-enabled context, which is wrong, and is the original
motivation for making this change.

Fixes: 3f518509

 ("ethernet: Add new driver for Marvell Armada 375 network unit")
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>