ice: split ice_discover_caps into two functions

Using the new ice_aq_list_caps and ice_parse_(dev|func)_caps functions,
replace ice_discover_caps with two functions that each take a pointer to
the dev_caps and func_caps structures respectively.

This makes the side effect of updating the hw->dev_caps and
hw->func_caps obvious from reading the implementation of the function.
Additionally, it opens the way for enabling reading of device
capabilities outside of the initialization flow. By passing in
a pointer, another caller will be able to read the capabilities without
modifying the HW capabilities structures.

As there are no other callers, it is safe to now remove
ice_aq_discover_caps and ice_parse_caps.

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>