iwlwifi: mvm: clean up LDBG config command usage

Clean up the LDBG config command to not be called "continuous
recording", and while at it actually remove the continuous
recording implementation completely since it was only used for
store & forward architectures.

This also fixes a bug at least in iwl_fw_dbg_buffer_allocation()
because what's now "__le32 type" (matching the firmware) used to
be "__le16 enable_recording", so the buffer allocation config
sub-struct would erroneously have started at the wrong offset.
In the other cases this didn't actually lead to a bug as other
bytes in pad[] were all zeroes, so accessing the 16-bit value as
a 32-bit value wouldn't make a difference (in little endian.)

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>