[PARISC] PDC_CHASSIS is implemented on all machines

This patch removes a limitation of the original code, so that CHASSIS
codes can be sent to all machines. On machines with a LCD panel, this
code displays "INI" during bootup, "RUN" when the system is booted and
running, "FLT" when a panic occurs, etc.

This part of the code can be enabled/disabled through CONFIG_PDC_CHASSIS

This patch also adds minimalistic support for Chassis warnings, through
a proc entry '/proc/chassis', which will reflect the warnings status (PSU
or fans failure when they happen, NVRAM battery level and temperature
thresholds overflows).

This part of the code can be enabled/disabled through CONFIG_PDC_CHASSIS_WARN

Signed-off-by: Thibaut VARENE <varenet@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>