wifi: ieee80211: add helper to validate ML element type and size

The helper functions to retrieve the EML capabilities and medium
synchronization delay both assume that the type is correct. Instead of
assuming the length is correct and still checking the type, add a new
helper to check both and don't do any verification.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230618214435.1b50e7a3b3cf.I9385514d8eb6d6d3c82479a6fa732ef65313e554@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>