env: Move envmatch() to env.h

Move envmatch() over to the new header file. Also rename it to env_match()
to better line up with other functions.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/examples/api/glue.c b/examples/api/glue.c
index 9c8ed8d..4086616 100644
--- a/examples/api/glue.c
+++ b/examples/api/glue.c
@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <env.h>
 #include <linux/types.h>
 #include <api_public.h>
 
@@ -365,7 +366,7 @@
 
 	/*
 	 * It's OK to pass only the name piece as last (and not the whole
-	 * 'name=val' string), since the API_ENUM_ENV call uses envmatch()
+	 * 'name=val' string), since the API_ENUM_ENV call uses env_match()
 	 * internally, which handles such case
 	 */
 	if (!syscall(API_ENV_ENUM, NULL, last, &env))