net: mvpp2: adjust the allocation/free of BM pools for PPv2.2

This commit adjusts the allocation and freeing of BM pools to support
PPv2.2. This involves:

 - Checking that the number of buffer pointers is a multiple of 16, as
   required by the hardware.

 - Adjusting the size of the DMA coherent area allocated for buffer
   pointers. Indeed, PPv2.2 needs space for 2 pointers of 64-bits per
   buffer, as opposed to 2 pointers of 32-bits per buffer in
   PPv2.1. The size in bytes is now stored in a new field of the
   mvpp2_bm_pool structure.

 - On PPv2.2, getting the DMA address and cookie (used for the physical
   address) of each buffer requires reading the
   MVPP22_BM_ADDR_HIGH_ALLOC to get the high order bits of those
   addresses. A new utility function mvpp2_bm_bufs_get_addrs() is
   introduced to handle this.

 - On PPv2.2, releasing a buffer requires writing the high order 32 bits
   of the DMA address and cookie to MVPP22_BM_PHY_VIRT_HIGH_RLS_REG.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>