fix[mpi]: Fix typo

Reported by cppcoffee@gmail.com
https://github.com/rockchip-linux/mpp/pull/824

Change-Id: I9df340bf14296cc70275c248494d1cc3249942d3
Signed-off-by: Herman Chen <herman.chen@rock-chips.com>

inc/mpp_frame.h

@@ -249,7 +249,7 @@ typedef enum {
 typedef enum {
     MPP_FMT_YUV420SP        = (MPP_FRAME_FMT_YUV + 0),  /* YYYY... UV... (NV12)     */
     /*
-     * A rockchip specific pixel format, without gap between pixel aganist
+     * A rockchip specific pixel format, without gap between pixel against
      * the P010_10LE/P010_10BE
      */
     MPP_FMT_YUV420SP_10BIT  = (MPP_FRAME_FMT_YUV + 1),