hpwdt: Only BYTE reads/writes to WD Timer port 0x72

This patch is to correct the use of the iLO port 0x72 usage.
The port 0x72 is a byte size write/read and hpwdt is currently
writing a WORD.

Signed-off by: Thomas Mingarelli <thomas.mingarelli@hp.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>