Fix acpica macros that subtract null pointers

Clang 13.0.0 produces a new -Werror warning about the ACPI_TO_INTEGER(p)
and ACPI_OFFSET(d, f) macros in acpica's actypes.h:

sys/contrib/dev/acpica

Fix acpica macros that subtract null pointers

Clang 13.0.0 produces a new -Werror warning about the ACPI_TO_INTEGER(p)
and ACPI_OFFSET(d, f) macros in acpica's actypes.h:

sys/contrib/dev/acpica/components/dispatcher/dsopcode.c:708:31: error: performing pointer subtraction with a null pointer has undefined behavior [-Werror,-Wnull-pointer-subtraction]
ObjDesc->Region.Address = ACPI_PTR_TO_PHYSADDR (Table);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~
sys/contrib/dev/acpica/include/actypes.h:664:41: note: expanded from macro 'ACPI_PTR_TO_PHYSADDR'
#define ACPI_PTR_TO_PHYSADDR(i) ACPI_TO_INTEGER(i)
^~~~~~~~~~~~~~~~~~
sys/contrib/dev/acpica/include/actypes.h:661:41: note: expanded from macro 'ACPI_TO_INTEGER'
#define ACPI_TO_INTEGER(p) ACPI_PTR_DIFF (p, (void *) 0)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
sys/contrib/dev/acpica/include/actypes.h:656:82: note: expanded from macro 'ACPI_PTR_DIFF'
#define ACPI_PTR_DIFF(a, b) ((ACPI_SIZE) (ACPI_CAST_PTR (UINT8, (a)) - ACPI_CAST_PTR (UINT8, (b))))
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

This problem of undefined behavior was also reported to acpica by @cem
in 2018: https://github.com/acpica/acpica/issues/407, but it seems there
was never any fix committed for it upstream.

Instead fix these locally, for ACPI_TO_INTEGER by simply casting the
incoming pointer to ACPI_SIZE (which corresponds roughly to uintptr_t
and size_t), and for ACPI_OFFSET by reusing our __offsetof definition
from sys/cdefs.h.

Reviewed by: emaste, kib, imp
Differential Revision: https://reviews.freebsd.org/D31710

(cherry picked from commit 130a690ae16e1b845629e586203b508eff699f38)

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