leds: lp50xx: Get rid of redundant explicit casting

In the line like

	u32 bar = ...;
	u8 foo = (u8)(bar >> 8) & 0xff;

is no need to have neither explicit casting nor ' & 0xff' part.
Get rid of them.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>