drivers/leds/leds-lp5521.c: perform SW reset before detection

Chip detection may fail if the chip is in some odd state for example after
system restart.  Chip doesn't have HW reset line.

Signed-off-by: Samu Onkalo <samu.p.onkalo@nokia.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>