leds: Small fixes for Flash class description

Fix misspelling and capitalization of LED in the Kconfig.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Dan Murphy <dmurphy@ti.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>