I420ToI010 fix for missing LIBYUV_API in DLL

Bug: libyuv:850
Change-Id: Ib10208955bd1b5614f9278fcbef2340bb7425888
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/1902252Reviewed-by: Dale Curtis <dalecurtis@chromium.org>

include/libyuv/convert_from.h

@@ -23,6 +23,7 @@ extern "C" {
 
 // Convert 8 bit YUV to 10 bit.
 #define H420ToH010 I420ToI010
+LIBYUV_API
 int I420ToI010(const uint8_t* src_y,
                int src_stride_y,
                const uint8_t* src_u,