[PARISC] HPPB bus updates for E-Class systems

This patch addresses the following issues:
   * Removes an incorrect comment.
   * Fixes a couple of compiler warnings.
   * Properly detects the HP-PB bus on E-Class systems.

Signed-off-by: Ryan Bradetich <rbrad@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>