Add the rss_configurable_function_key bit to driver_supported_feature.

This bit tells the device that the driver in question supports the
retrieving and updating of RSS function and hash key, and therefore
the device should allow RSS function and key manipulation.

This commit turns on  device support for hash key and RSS function
management. Without this commit this feature is turned off at the
device and appears to the user as unsupported.

This commit concludes the following series of already merged commits:
commit 0af3c4e2 ("net: ena: changes to RSS hash key allocation")
commit c1bd17e5 ("net: ena: change default RSS hash function to Toeplitz")
commit f66c2ea3 ("net: ena: allow setting the hash function without changing the key")
commit e9a1de37 ("net: ena: fix error returning in ena_com_get_hash_function()")
commit 80f8443f ("net: ena: avoid unnecessary admin command when RSS function set fails")
commit 6a4f7dc8 ("net: ena: rss: do not allocate key when not supported")
commit 0d1c3de7 ("net: ena: fix incorrect default RSS key")

The above commits represent the last part of the implementation of
this feature, and with them merged the feature can be enabled
in the device.
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>