env: Inline env_get_char() into its only user

This function is a relic from the past when environment was read from
underlying device one character at a time.

It is used only in the case when getting an environemnt variable prior
relocation, and the function is simple enough to be inlined there.

Since env_get_char() is being changed to simple access to an array, we
can drop the failing cases and simplify the code (this could have been
done before, since env_get_char() did not fail even before).

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Simon Glass <sjg@chromium.org>

env/nowhere.c

@@ -31,9 +31,8 @@ static int env_nowhere_init(void)
 static int env_nowhere_load(void)
 {
 	/*
-	 * for SPL, set env_valid = ENV_INVALID is enough as env_get_char()
-	 * return the default env if env_get is used
-	 * and SPL don't used env_import to reduce its size
+	 * For SPL, setting env_valid = ENV_INVALID is enough, as env_get()
+	 * searches default_environment array in that case.
 	 * For U-Boot proper, import the default environment to allow reload.
 	 */
 	if (!IS_ENABLED(CONFIG_SPL_BUILD))