Fix iconv_open(3) docs.

Strictly the _doc comment_ is correct, but the names of the parameters
are the wrong way round. (Although iconv_open() follows the usual C
tradition of "destination first", iconv() itself doesn't, so these
functions are inherently confused/confusing.)

Bug: https://github.com/android/ndk/issues/1895
Test: N/A
Change-Id: Iafc9bd630ece1d3c55986b04bb9a99c477716530
diff --git a/libc/include/iconv.h b/libc/include/iconv.h
index 7cf36dc..794a292 100644
--- a/libc/include/iconv.h
+++ b/libc/include/iconv.h
@@ -54,7 +54,7 @@
  *
  * Available since API level 28.
  */
-iconv_t _Nonnull iconv_open(const char* _Nonnull __src_encoding, const char* _Nonnull __dst_encoding) __INTRODUCED_IN(28);
+iconv_t _Nonnull iconv_open(const char* _Nonnull __dst_encoding, const char* _Nonnull __src_encoding) __INTRODUCED_IN(28);
 
 /**
  * [iconv(3)](http://man7.org/linux/man-pages/man3/iconv.3.html) converts characters from one