ACPI: disable -Wstringop-truncation

ACPI: disable -Wstringop-truncation

gcc -Wstringop-truncation warns about copying a string that results in a
missing nul termination:

drivers/acpi/acpica/tbfind.c: In function 'acpi_tb_find_table':
drivers/acpi/acpica/tbfind.c:60:9: error: 'strncpy' specified bound 6 equals destination size [-Werror=stringop-truncation]
   60 |         strncpy(header.oem_id, oem_id, ACPI_OEM_ID_SIZE);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/acpi/acpica/tbfind.c:61:9: error: 'strncpy' specified bound 8 equals destination size [-Werror=stringop-truncation]
   61 |         strncpy(header.oem_table_id, oem_table_id, ACPI_OEM_TABLE_ID_SIZE);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The code works as intended, and the warning could be addressed by using
a memcpy(), but turning the warning off for this file works equally well
and may be easier to merge.

Fixes: 47c08729bf1c ("ACPICA: Fix for LoadTable operator, input strings")
Link: https://lore.kernel.org/lkml/CAJZ5v0hoUfv54KW7y4223Mn9E7D4xvR7whRFNLTBqCZMUxT50Q@mail.gmail.com/#t
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>