Add a driver for the SGMICRO SGM3140 Buck/Boost Charge Pump LED driver.
This device is controller by two GPIO lines, one for enabling the LED
and the second one for switching between torch and flash mode.
The device will automatically switch to torch mode after being in flash
mode for about 250-300ms, so after that time the driver will turn the
LED off again automatically.
Signed-off-by: Luca Weiss <luca@xxxxxxxxx>
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