chromeos-bsp-daisy: create /dev/rtc symlink.

There are two viable PMIC options for the Exynos 5250: max77686 &
s5m8767.  Both contain RTCs that can be backed by battery/coin cell to
keep time across shutdowns.

CL includes those udev rules in one file.

BUG=chrome-os-partner:19036
TEST=manual,

  emerge-daisy chromeos-bsp-daisy
  emerge-daisy_spring chromeos-bsp-daisy
  USE=-snow emerge-daisy chromeos-bsp-daisy

All build successfully.  In the case of USE=-snow files are NOT installed.

Install file on Snow and Spring and reboot.  Then:

On spring:
----------
udevadm info --query=all --name=rtc
P: /devices/s3c2440-i2c.0/i2c-0/0-0066/s5m-rtc/rtc/rtc1
N: rtc1
S: rtc
E: UDEV_LOG=3
E: DEVPATH=/devices/s3c2440-i2c.0/i2c-0/0-0066/s5m-rtc/rtc/rtc1
E: MAJOR=254
E: MINOR=1
E: DEVNAME=/dev/rtc1
E: SUBSYSTEM=rtc
E: DEVLINKS=/dev/rtc

On snow:
--------
udevadm info --query=all --name=rtc
P: /devices/s3c2440-i2c.0/i2c-0/0-0009/max7768-rtc/rtc/rtc0
N: rtc0
S: rtc
E: UDEV_LOG=3
E: DEVPATH=/devices/s3c2440-i2c.0/i2c-0/0-0009/max7768-rtc/rtc/rtc0
E: MAJOR=254
E: MINOR=1
E: DEVNAME=/dev/rtc0
E: SUBSYSTEM=rtc
E: DEVLINKS=/dev/rtc

Change-Id: I2ce54c0a4bf6d6d00b011a41f43c4ba899f05dc8
Reviewed-on: https://gerrit.chromium.org/gerrit/49996
Commit-Queue: Todd Broch <tbroch@chromium.org>
Reviewed-by: Todd Broch <tbroch@chromium.org>
Tested-by: Todd Broch <tbroch@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
(cherry picked from commit cc3801bccb79e430f845af887e8266ca028b967b)
Reviewed-on: https://gerrit.chromium.org/gerrit/50927
4 files changed