nfp: add TLV capabilities to the BAR

NFP is entirely programmable, including the PCI data interface.
Using a fixed control BAR layout certainly makes implementations
easier, but require careful considerations when space is allocated.
Once BAR area is allocated to one feature nothing else can use it.
Allocating space statically also requires it to be sized upfront,
which leads to either unnecessary limitation or wastage.

We currently have a 32bit capability word defined which tells drivers
which application FW features are supported.   Most of the bits
are exhausted.  The same bits are also reused for enabling specific
features.  Bulk of capabilities don't have a need for an enable bit,
however, leading to confusion and wastage.

TLVs seems like a better fit for expressing capabilities of applications
running on programmable hardware.

This patch leaves the front of the BAR as is, and declares a TLV
capability start at offset 0x58.  Most of the space up to 0x0d90
is already allocated, but the used space can be wrapped with RESERVED
TLVs.  E.g.:

Address    Type         Length
 0x0058    RESERVED      0xe00  /* Wrap basic structures */
 0x0e5c    FEATURE_A     0x004
 0x0e64    FEATURE_B     0x004
 0x0e6c    RESERVED      0x990  /* Wrap qeueue stats */
 0x1800    FEATURE_C     0x100

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>