Documentation: hisi-pmu: Drop reference to /sys/devices path

Documentation: hisi-pmu: Drop reference to /sys/devices path

Having assigned a parent to the device, the suggested path is
no longer valid.  As /sys/bus/event_sources based path is also
provided, simply drop mention of alternative.

Reviewed-by: Yicong Yang <yangyicong@hisilicon.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20240412161057.14099-3-Jonathan.Cameron@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>