Revert "mtd: spi-nor: Prefer asynchronous probe"

This reverts commit 03edda0e

.

This leads to warn dump like [1] on some platforms and reorders MTD
devices which may break user space expectations [2]. So revert the change.

[1]:

[    1.849801] ------------[ cut here ]------------
[    1.854271] mscc_felix 0000:00:00.5: device is disabled, skipping
[    1.858753] WARNING: CPU: 1 PID: 7 at kernel/kmod.c:136 __request_module+0x3a4/0x568

[...]

[2] Bug report: https://lore.kernel.org/linux-mtd/20201003150633.23416-1-michael@walle.cc/

Reported-by: Michael Walle <michael@walle.cc>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20201005090321.8724-1-vigneshr@ti.com