fbdev/broadsheetfb: fix memory leak

static code analysis from cppcheck reports:

[drivers/video/fbdev/broadsheetfb.c:673]:
(error) Memory leak: sector_buffer

sector_buffer is not being kfree'd on each call to
broadsheet_spiflash_rewrite_sector(), so free it.

Signed-off-by: Colin Ian King <[e-mail]>
Signed-off-by: Tomi Valkeinen <[e-mail]>

drivers/video/fbdev/broadsheetfb.c

···
 		err = broadsheet_spiflash_read_range(par, start_sector_addr,
 						data_start_addr, sector_buffer);
 		if (err)
-			return err;
+			goto out;
 	}
 
 	/* now we copy our data into the right place in the sector buffer */
···
 		err = broadsheet_spiflash_read_range(par, tail_start_addr,
 			tail_len, sector_buffer + tail_start_addr);
 		if (err)
-			return err;
+			goto out;
 	}
 
 	/* if we got here we have the full sector that we want to rewrite. */
···
 	/* first erase the sector */
 	err = broadsheet_spiflash_erase_sector(par, start_sector_addr);
 	if (err)
-		return err;
+		goto out;
 
 	/* now write it */
 	err = broadsheet_spiflash_write_sector(par, start_sector_addr,
 					sector_buffer, sector_size);
+out:
+	kfree(sector_buffer);
 	return err;
 }