video: goldfishfb: fix memory leak on driver remove

goldfish_fb_probe() allocates memory for fb, but goldfish_fb_remove() does
not have deallocation of fb, which leads to memory leak on probe/remove.

The patch adds deallocation into goldfish_fb_remove().

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Anton Vasilyev <vasilyev@ispras.ru>
Cc: Aleksandar Markovic <aleksandar.markovic@mips.com>
Cc: Miodrag Dinic <miodrag.dinic@mips.com>
Cc: Goran Ferenc <goran.ferenc@mips.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>