platform/x86: x86-android-tablets: Fix an IS_ERR() vs NULL check in probe

The spi_new_device() function returns NULL on error, it doesn't return
error pointers.

Fixes: 70505ea6 ("platform/x86: x86-android-tablets: Add support for SPI device instantiation")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/4b1b2395-c7c5-44a4-b0b0-6d091c7f46a2@moroto.mountain


Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>