rk1000: fix create sysfs file permission error.
Wrong permission will case following warning:
------------[ cut here ]------------
WARNING: at drivers/base/core.c:576 device_create_file+0x74/0xa4()
Attribute rkcontrl: write permission without 'store'
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.10.0 #247
Call trace:
[<
ffffffc000087dc0>] dump_backtrace+0x0/0x10c
[<
ffffffc000087edc>] show_stack+0x10/0x1c
[<
ffffffc00087c0e4>] dump_stack+0x1c/0x28
[<
ffffffc0000a1b08>] warn_slowpath_common+0x74/0x9c
[<
ffffffc0000a1b7c>] warn_slowpath_fmt+0x4c/0x58
[<
ffffffc00036cfec>] device_create_file+0x70/0xa4
[<
ffffffc000399fc4>] rk1000_probe+0x1d0/0x20c
[<
ffffffc00058b190>] i2c_device_probe+0x9c/0xd4
[<
ffffffc000370e70>] driver_probe_device+0xd0/0x210
[<
ffffffc00037105c>] __driver_attach+0x60/0x90
[<
ffffffc00036f394>] bus_for_each_dev+0x60/0x88
[<
ffffffc00037096c>] driver_attach+0x1c/0x28
[<
ffffffc000370540>] bus_add_driver+0xf4/0x210
[<
ffffffc000371698>] driver_register+0xbc/0x138
[<
ffffffc00058b054>] i2c_register_driver+0x48/0xac
[<
ffffffc000bf2934>] rk1000_init+0x14/0x20
[<
ffffffc000081554>] do_one_initcall+0x80/0x120
[<
ffffffc000bdb8f0>] kernel_init_freeable+0x148/0x1e8
[<
ffffffc000876a10>] kernel_init+0x10/0xcc
---[ end trace
1cc1e45d37744cff ]---
Signed-off-by: Zheng Yang <zhengyang@rock-chips.com>