iwlwifi: dbg: split iwl_fw_error_dump to two functions

Split iwl_fw_error_dump to two parts.  The first part will dump the
actual data, and second will do the file allocations, trans calls and
actual file operations.  This is done in order to enable reuse of the
code for the new debug ini infrastructure.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>