ACPICA: ACPI 6.0: Add ACPI_SUB_PTR().

ACPICA commit 5de82757aef5d6163e37064033aacbce193abbca

Using a minus number with ACPI_ADD_PTR() will cause compiler warnings, such
warnings cannot be eliminated by force casting an unsigned value to a
signed value. This patch thus introduces ACPI_SUB_PTR() to be used with
minus numbers. Lv Zheng.

Link: https://github.com/acpica/acpica/commit/5de82757Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/acpi/actypes.h

@@ -525,6 +525,7 @@ typedef u64 acpi_integer;
 #define ACPI_CAST_PTR(t, p)             ((t *) (acpi_uintptr_t) (p))
 #define ACPI_CAST_INDIRECT_PTR(t, p)    ((t **) (acpi_uintptr_t) (p))
 #define ACPI_ADD_PTR(t, a, b)           ACPI_CAST_PTR (t, (ACPI_CAST_PTR (u8, (a)) + (acpi_size)(b)))
+#define ACPI_SUB_PTR(t, a, b)           ACPI_CAST_PTR (t, (ACPI_CAST_PTR (u8, (a)) - (acpi_size)(b)))
 #define ACPI_PTR_DIFF(a, b)             (acpi_size) (ACPI_CAST_PTR (u8, (a)) - ACPI_CAST_PTR (u8, (b)))
 
 /* Pointer/Integer type conversions */