xgetXXbyYY: Simplify elifs

-  Use SIZE_MAX rather than (size_t)-1, to improve readability.

-  Move the only branch that breaks to the first place, so that we
   remove an else.  This reduces nesting while parsing the code.

-  Now that we only have a 2-branch conditional where both branches
   assign to the same variable, rewrite it as a ternary, to shorten.

Signed-off-by: Alejandro Colomar <alx@kernel.org>

libmisc/xgetXXbyYY.c

@@ -79,13 +79,11 @@
 			break;
 		}
 
-		if (length <= ((size_t)-1 / 4)) {
-			length *= 4;
-		} else if (length == (size_t) -1) {
+		if (length == SIZE_MAX) {
 			break;
-		} else {
-			length = (size_t) -1;
 		}
+
+		length = (length <= SIZE_MAX / 4) ? length * 4 : SIZE_MAX;
 	}
 
 	free(buffer);