avifFillAlpha and avifReformatAlpha do not need a return value. (#1656)

diff --git a/include/avif/internal.h b/include/avif/internal.h
index 2d93238..af490e9 100644
--- a/include/avif/internal.h
+++ b/include/avif/internal.h

@@ -137,8 +137,8 @@
 
 } avifAlphaParams;
 
-avifBool avifFillAlpha(const avifAlphaParams * params);
-avifBool avifReformatAlpha(const avifAlphaParams * params);
+void avifFillAlpha(const avifAlphaParams * params);
+void avifReformatAlpha(const avifAlphaParams * params);
 
 typedef enum avifReformatMode
 {

diff --git a/src/alpha.c b/src/alpha.c
index 3b7baea..97ed2c4 100644
--- a/src/alpha.c
+++ b/src/alpha.c

@@ -6,7 +6,7 @@
 #include <assert.h>
 #include <string.h>
 
-avifBool avifFillAlpha(const avifAlphaParams * params)
+void avifFillAlpha(const avifAlphaParams * params)
 {
     if (params->dstDepth > 8) {
         const uint16_t maxChannel = (uint16_t)((1 << params->dstDepth) - 1);
@@ -28,10 +28,9 @@
             }
         }
     }
-    return AVIF_TRUE;
 }
 
-avifBool avifReformatAlpha(const avifAlphaParams * params)
+void avifReformatAlpha(const avifAlphaParams * params)
 {
     const int srcMaxChannel = (1 << params->srcDepth) - 1;
     const int dstMaxChannel = (1 << params->dstDepth) - 1;
@@ -113,8 +112,6 @@
             }
         }
     }
-
-    return AVIF_TRUE;
 }
 
 avifResult avifRGBImagePremultiplyAlpha(avifRGBImage * rgb)

diff --git a/src/reformat.c b/src/reformat.c
index a9ac0a8..b4d63ba 100644
--- a/src/reformat.c
+++ b/src/reformat.c

@@ -495,11 +495,11 @@
             params.srcOffsetBytes = state.rgb.offsetBytesA;
             params.srcPixelBytes = state.rgb.pixelBytes;
 
-            AVIF_CHECKERR(avifReformatAlpha(&params), AVIF_RESULT_REFORMAT_FAILED);
+            avifReformatAlpha(&params);
         } else {
             // libyuv does not fill alpha when converting from RGB to YUV so
             // fill it regardless of the value of convertedWithLibYUV.
-            AVIF_CHECKERR(avifFillAlpha(&params), AVIF_RESULT_REFORMAT_FAILED);
+            avifFillAlpha(&params);
         }
     }
     return AVIF_RESULT_OK;
@@ -1357,9 +1357,9 @@
             params.srcOffsetBytes = 0;
             params.srcPixelBytes = state->yuv.channelBytes;
 
-            AVIF_CHECKERR(avifReformatAlpha(&params), AVIF_RESULT_REFORMAT_FAILED);
+            avifReformatAlpha(&params);
         } else {
-            AVIF_CHECKERR(avifFillAlpha(&params), AVIF_RESULT_REFORMAT_FAILED);
+            avifFillAlpha(&params);
         }
     }