ARM: 7697/1: hw_breakpoint: do not use __cpuinitdata for dbg_cpu_pm_nb

We must not declare dbg_cpu_pm_nb as __cpuinitdata as we need it after
system initialization for Suspend and CPUIdle.

This was done in commit 9a6eb310 ("ARM: hw_breakpoint: Debug powerdown
support for self-hosted debug").

Cc: stable@vger.kernel.org
Cc: Dietmar Eggemann <Dietmar.Eggemann@arm.com>
Signed-off-by: Bastian Hecht <hechtb+renesas@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>