slw: Change variable name can_winkle to has_slw
slw: Change variable name can_winkle to has_slw

Change variable name "can_winkle" to a more generic name "has_slw". This
makes it easier to add new deep-idle states which rely on SLW.

Acked-by: Michael Neuling <7b0ab45a730e48a69239010b5b8fe5fa4e8eaac6@neuling.org>
Signed-off-by: Shreyas B. Prabhu <fac76aafe57fc9acb24e05f5dba9b58a43a0a645@linux.vnet.ibm.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

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