slw: Fix parsing of supported STOP states
slw: Fix parsing of supported STOP states

Bits[0-15] are used to indicate the supported STOP states in
"ibm,enabled-stop-levels" DT property and STOP0 is starting from
Bit0. This patch fixes the parsing to read the appropriate bits.

Fixes: c3ea33f173ec ("hw/slw: only enable supported STOP states")
Signed-off-by: Shilpasri G Bhat <d5e9f39adad3a1ae2ac6557cc4305369c013b729@linux.vnet.ibm.com>
Reviewed-by: Oliver O'Halloran <3dfaff8fa6ae977f042064a112a6aac576279b9b@gmail.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

shenki/skiboot,stewart-ibm/skiboot,legoater/skiboot,stewart-ibm/skiboot,qemu/skiboot,open-power/skiboot,stewart-ibm/skiboot,qemu/skiboot,legoater/skiboot,shenki/skiboot,mikey/skiboot,legoater/skiboot,shenki/skiboot,mikey/skiboot,legoater/skiboot,shenki/skiboot,open-power/skiboot,open-power/skiboot,mikey/skiboot,qemu/skiboot,legoater/skiboot,qemu/skiboot,open-power/skiboot,open-power/skiboot,shenki/skiboot,qemu/skiboot