Refactor some alignment handling

Made using coccinelle:
  @@
  expression E;
  @@
  -(E + 7) & -8
  +ALIGN(E, 8)

  @@
  expression E;
  @@
  -(E + 15) & -16
  +ALIGN(E, 16)

Change-Id: I071d2c98cd95580d7de21d256c31b6368a3dc70b
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/910
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/mainboard/aopen/dxplplusu/acpi_tables.c

@@ -92,7 +92,7 @@ unsigned long acpi_fill_madt(unsigned long current)
 	return current;
 }
 
-#define ALIGN_CURRENT current = ((current + 0x0f) & -0x10)
+#define ALIGN_CURRENT current = (ALIGN(current, 16))
 unsigned long write_acpi_tables(unsigned long start)
 {
 	unsigned long current;