Use positive logic (pm_up instead of pm_down) to check whether PMU
services are available. This change also puts the variable into the
BSS section rather than the Data section as the variable is now
initialized to 0 rather than 1.

Signed-off-by: Will Wong <WILLW@xilinx.com>
Signed-off-by: Stefan Krsmanovic <stefan.krsmanovic@aggios.com>
Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>