ACPI: Clarify resource conflict message

The message "ACPI: Device needs an ACPI driver" is misleading. The
device _may_ need an ACPI driver, if the BIOS implemented a custom
API for the device in question (which, AFAIK, can't be checked.) If
not, then either a generic ACPI driver may be used (for example
"thermal"), or nothing can be done (other than a white list).

I propose to reword the message to:

ACPI: If an ACPI driver is available for this device, you should use
it instead of the native driver

which I think is more correct. Comments and suggestions welcome.

I also added a message warning about possible problems and system
instability when users pass acpi_enforce_resources=lax, as suggested
by Len.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Thomas Renninger <trenn@suse.de>
Cc: Alan Jenkins <sourcejedi.lkml@googlemail.com>
Signed-off-by: Len Brown <len.brown@intel.com>