ACPI / PNP: Fix acpi_pnp_match()

The acpi_pnp_match() function is used for finding the ACPI device
object that should be associated with the given PNP device.
Unfortunately, the check used by that function is not strict enough
and may cause success to be returned for a wrong ACPI device object.

To fix that, use the observation that the pointer to the ACPI
device object in question is already stored in the data field
in struct pnp_dev, so acpi_pnp_match() can simply use that
field to do its job.

This problem was uncovered in 3.14 by commit 202317a573b2 (ACPI / scan:
Add acpi_device objects for all device nodes in the namespace).

Fixes: 202317a573b2 (ACPI / scan: Add acpi_device objects for all device nodes in the namespace)
Reported-and-tested-by: Vinson Lee <vlee@twopensource.com>
Cc: 3.14+ <stable@vger.kernel.org> # 3.14+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Merge back earlier acpi-pnp material.

Conflicts:
	drivers/pnp/pnpacpi/core.c
ACPI / PNP: Replace faulty is_hex_digit() by isxdigit()

0 is ascii for NULL. Hex digit matching should be from '0'.
Faulty version returns true for #,$,%,& etc.

Signed-off-by: Arjun Sreedharan <arjun024@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Merge branch 'acpi-pnp' into linux-next

* acpi-pnp:
  ACPI / PNP: Replace faulty is_hex_digit() by isxdigit()
  ACPI / PNP: Fix acpi_pnp_match()