leds: qti-tri-led: Control BOB_CONFIG_EXT_CTRL2_FORCE_EN for HR_LED

As per the hardware recommendation, BOB_CONFIG_EXT_CTRL2_FORCE_EN
needs to be controlled before enabling or disabling HR_LEDs.
Add support for that by doing PBS trigger through SDAM which is
available as a nvmem device.

Change-Id: Iaae6f5b86c7db014c2cbdf53054d7e3ac869c283
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>