ACPICA: Use uintptr_t and offsetof() in Linux kernel builds

To avoid "performing pointer subtraction with a null pointer has
undefined behavior" compiler warnings, use uintptr_t and offsetof()
that are always available during Linux kernel builds to define
acpi_uintptr_t and the ACPI_TO_INTEGER() and ACPI_OFFSET() macros.

Based on earlier proposal from Arnd Bergmann.

Link: https://lore.kernel.org/linux-acpi/20210927121338.938994-1-arnd@kernel.org
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

include/acpi/actypes.h

@@ -507,8 +507,12 @@ typedef u64 acpi_integer;
 /* Pointer/Integer type conversions */
 
 #define ACPI_TO_POINTER(i)              ACPI_CAST_PTR (void, (acpi_size) (i))
+#ifndef ACPI_TO_INTEGER
 #define ACPI_TO_INTEGER(p)              ACPI_PTR_DIFF (p, (void *) 0)
+#endif
+#ifndef ACPI_OFFSET
 #define ACPI_OFFSET(d, f)               ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
+#endif
 #define ACPI_PTR_TO_PHYSADDR(i)         ACPI_TO_INTEGER(i)
 
 /* Optimizations for 4-character (32-bit) acpi_name manipulation */

include/acpi/platform/aclinux.h

@@ -114,6 +114,11 @@
 #define acpi_raw_spinlock                   raw_spinlock_t *
 #define acpi_cpu_flags                      unsigned long
 
+#define acpi_uintptr_t                      uintptr_t
+
+#define ACPI_TO_INTEGER(p)                  ((uintptr_t)(p))
+#define ACPI_OFFSET(d, f)                   offsetof(d, f)
+
 /* Use native linux version of acpi_os_allocate_zeroed */
 
 #define USE_NATIVE_ALLOCATE_ZEROED