msm: pm-8x60: Initialize attributes with sysfs_attr_init()

These sysfs attributes are generated dynamically and thus need to
be initialized with sysfs_attr_init() to avoid warnings such as:

	BUG: key ef15ff8c not in .data!

which occur if lockdep is enabled.

Change-Id: I81145da5c2be7b81ba64302730856331e8ea8cf4
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>