patch 9.0.1166: code is indented more than necessary

Problem:    Code is indented more than necessary.
Solution:   Use an early return where it makes sense. (Yegappan Lakshmanan,
            closes #11792)
diff --git a/src/filepath.c b/src/filepath.c
index 023c732..be1a581 100644
--- a/src/filepath.c
+++ b/src/filepath.c
@@ -3084,13 +3084,13 @@
     char_u  *dest;
 
     dest = alloc(STRLEN(fname1) + STRLEN(fname2) + 3);
-    if (dest != NULL)
-    {
-	STRCPY(dest, fname1);
-	if (sep)
-	    add_pathsep(dest);
-	STRCAT(dest, fname2);
-    }
+    if (dest == NULL)
+	return NULL;
+
+    STRCPY(dest, fname1);
+    if (sep)
+	add_pathsep(dest);
+    STRCAT(dest, fname2);
     return dest;
 }
 
@@ -3122,14 +3122,14 @@
 	return NULL;
 
     buf = alloc(MAXPATHL);
-    if (buf != NULL)
-    {
-	if (vim_FullName(fname, buf, MAXPATHL, force) != FAIL)
-	    new_fname = vim_strsave(buf);
-	else
-	    new_fname = vim_strsave(fname);
-	vim_free(buf);
-    }
+    if (buf == NULL)
+	return NULL;
+
+    if (vim_FullName(fname, buf, MAXPATHL, force) != FAIL)
+	new_fname = vim_strsave(buf);
+    else
+	new_fname = vim_strsave(fname);
+    vim_free(buf);
     return new_fname;
 }