sk98lin: kill bogus check and convert to use ARRAY_SIZE()

This converts uses of ARRAY_SIZE(), and while at it also kills
unreachable code as far as I can say. I can't tell what was the author
trying to do with the following check. First we have:

PNMI_STATIC const SK_PNMI_STATADDR
		StatAddr[SK_PNMI_MAX_IDX][SK_PNMI_MAC_TYPES];

and then a check goes like this:

if (SK_PNMI_MAX_IDX !=
   (sizeof(StatAddr) / (sizeof(SK_PNMI_STATADDR) * SK_PNMI_MAC_TYPES)))

with the second line being just ARRAY_SIZE(StatAddr), which will always
return SK_PNMI_MAX_IDX, rendering the check useless.

Signed-off-by: Alejandro Martinez Ruiz <alex@flawedcode.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>