ARM: 6074/1: oprofile: convert from sysdev to platform device

This is a reworking of an original patch posted by Aaro Koskinen:

oprofile does not work with PM, because sysdev_suspend() is done with
interrupts disabled and oprofile needs a mutex. Implementing oprofile
as a platform device solves this problem.

Cc: Aaro Koskinen <aaro.koskinen@nokia.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>