drm/omap: silence unititialized variable warning

Smatch complains that "area_free" could be used without being
initialized.  This code is several years old and premusably works fine
so this can't be a very serious bug.  But it's easy enough to silence
the warning.  If "area_free" is false at the end of the function then
we return -ENOMEM.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180418142937.GA13828@mwandaSigned-off-by: Sean Paul <seanpaul@chromium.org>

drivers/gpu/drm/omapdrm/tcm-sita.c

@@ -90,7 +90,7 @@ static int l2r_t2b(u16 w, u16 h, u16 a, s16 offset,
 {
 	int i;
 	unsigned long index;
-	bool area_free;
+	bool area_free = false;
 	unsigned long slots_per_band = PAGE_SIZE / slot_bytes;
 	unsigned long bit_offset = (offset > 0) ? offset / slot_bytes : 0;
 	unsigned long curr_bit = bit_offset;