ice: refactor ice_discover_caps to avoid need to retry

The ice_discover_caps function is used to read the device and function
capabilities, updating the hardware capabilities structures with
relevant data.

The exact number of capabilities returned by the hardware is unknown
ahead of time. The AdminQ command will report the total number of
capabilities in the return buffer.

The current implementation involves requesting capabilities once,
reading this returned size, and then re-requested with that size.

This isn't really necessary. The firmware interface has a maximum size
of ICE_AQ_MAX_BUF_LEN. Firmware can never return more than
ICE_AQ_MAX_BUF_LEN / sizeof(struct ice_aqc_list_caps_elem) capabilities.

Avoid the retry loop by simply allocating a buffer of size
ICE_AQ_MAX_BUF_LEN. This is significantly simpler than retrying. The
extra allocation isn't a big deal, as it will be released after we
finish parsing the capabilities.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>