fix Makefile chmod (644)
replace MD5SUM with HASH
add PKG_MIRROR_HASH when PKG_SOURCE_PROTO:=git

(PKG_SOURCE_PROTO:=svn tarballs are not reproducible for now)

Signed-off-by: Etienne Champetier <champetier.etienne@gmail.com>

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

Maintainer: @nwf
Compile tested: LEDE HEAD ar71xx
Run tested: LEDE HEAD on ar71xx, basic functionality testing

Description: A minimal kermit file transfer program

Signed-off-by: Nathaniel Wesley Filardo <nwfilardo@gmail.com>