bnxt_en: Add logical RSS indirection table structure.

The driver currently does not keep track of the logical RSS indirection
table.  The hardware RSS table is set up with standard default ring
distribution when initializing the chip.  This makes it difficult to
support user sepcified indirection table entries.  As a first step, add
the logical table in the main bnxt structure and allocate it according
to chip specific table size.  Add a function that sets up default
RSS distribution based on the number of RX rings.

v4: Use bnxt_get_rxfh_indir_size() for the current RSS table size.

v2: Use kmalloc_array() since we init. all entries afterwards.
    Use ALIGN() to roundup the RSS table size.
    Use ethtool_rxfh_indir_default() to init. the default entries.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>