vp8: [loongson] fix bug of type conflict.

In commit 577d4fa79, int8_t was used to replace char. This will result in a
compilation error, for int8_t was typedefined to signed char, but not char.

Change-Id: I5c9837e01b0b58688a7741f5c9a99a76ca887e4a
1 file changed