If the ACPI register bit width is zero (an invalid value) assume it is the
default spacing.  This avoids some coredumps on invalid data and makes some
systems work that have broken ACPI data.

Signed-off-by: Corey Minyard <minyard@acm.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>