Correct if statements in mainpage.dox

Fixed if statements used in mainpage.dox.

BUG=aomedia:2674

Change-Id: I0f2659659a68fee35371bad7191a16ec08d90d8e
diff --git a/mainpage.dox b/mainpage.dox
index 03a299a..f34c61f 100644
--- a/mainpage.dox
+++ b/mainpage.dox
@@ -1,4 +1,4 @@
-/*!\mainpage AMedia Codec SDK
+/*!\mainpage AOMedia Codec SDK
 
   \section main_contents Page Contents
   - \ref main_intro
@@ -6,15 +6,15 @@
   - \ref main_support
 
   \section main_intro Introduction
-  Welcome to the AMedia Codec SDK. This SDK allows you to integrate your
+  Welcome to the AOMedia Codec SDK. This SDK allows you to integrate your
   applications with the AOM and AV1 video codecs.
 
   This distribution of the AOMedia Codec SDK includes the following support:
 
-  \if aom_encoder
+  \if av1_encoder
   - \ref aom_encoder
   \endif
-  \if aom_decoder
+  \if av1_decoder
   - \ref aom_decoder
   \endif