The comment about return value of acpi_table_parse() is incorrect.
This patch fix it.

Since all callers only check if the function succeeded or not, this
patch simplifies the semantics by returning -errno for all failure
cases. This will also simply the comment.

As suggested by Toshi Kani <toshi.kani@hp.com>, also change the stub
in linux/acpi.h to return -ENODEV.
Signed-off-by: NTang Chen <tangchen@cn.fujitsu.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>