video: vesa_fb: Fix wrong return value check of pci_find_class()

When pci_find_class() fails to find a device, it returns -ENODEV.
But now we check the return value against -1. Fix it.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
Acked-by: Anatolij Gustschin <agust@denx.de>