blame: report correct number of lines in progress when using ranges

blame: report correct number of lines in progress when using ranges

When using ranges, use the range sizes as the limit for progress
instead of the size of the full file.

Before:
$ git blame --progress builtin/blame.c > /dev/null
Blaming lines: 100% (1210/1210), done.
$ git blame --progress -L 100,120 -L 200,300 builtin/blame.c > /dev/null
Blaming lines:  10% (122/1210), done.
$

After:
$ ./git blame --progress builtin/blame.c > /dev/null
Blaming lines: 100% (1210/1210), done.
$ ./git blame --progress -L 100,120 -L 200,300 builtin/blame.c > /dev/null
Blaming lines: 100% (122/122), done.
$

Signed-off-by: Edmundo Carmona Antoranz <eantoranz@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>