Many (all?) of the coefficients related to calculating the
correct temperature are signed integers

This patch correcly parses and stores those values
It also ensures that the default offset is 0 (previously 1)

Affected cards - the original nv50 and the nv40 family
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>