Fix BM homebrew compatibility (rptrid comparison)
Fix BM homebrew compatibility (rptrid comparison)

BM switched from upper case to lower case hexadecimal representation in
BrandMeister release 20190421-185653.

The comparison must be case insensitive according to a member of the BM
dev team (@cyanide-burnout) on Telegram:
"it shoud check on case-insensetive way".

pd0mz/go-dmr