drivers/leds/leds-lp5521.c: check if reset is successful

drivers/leds/leds-lp5521.c: check if reset is successful

Make sure that the reset is successful by issuing a dummy read to R
channel current register and check its default value.  On some platforms,
without this dummy read, any further access to {R/G/B}_EXEC will not have
any impact.

Signed-off-by: srinidhi kasagar <srinidhi.kasagar@stericsson.com>
Tested-by: Naga Radhesh <naga.radheshy@stericsson.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>