reglib bugs

Some simple bugs I found by inspection:

- reglib_parse_country_dfs() always overflows the alpha2[] array by one
byte as sscanf() will write a terminating null byte.

- reglib_parse_country_dfs() can overflow the dfs_region_alpha[] array,
given invalid input.  If the input is always trusted then this may not
matter.

- reglib_deduce_band() can never return 60 (GHz) as the 5 GHz condition
will have been matched already.

- reg_rule_optimize_rd() has a bounds check on rule_idx but it's
off-by-one.

Ben.

-- 
Ben Hutchings
One of the nice things about standards is that there are so many of them.