mtd: cqspi: Simplify indirect read code

The indirect read code is a pile of nastiness. This patch replaces
the whole unmaintainable indirect read implementation with the one
from upcoming Linux CQSPI driver, which went through multiple rounds
of thorough review and testing. All the patch does is it plucks out
duplicate ad-hoc code distributed across the driver and replaces it
with more compact code doing exactly the same thing. There is no
speed change of the read operation.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Anatolij Gustschin <agust@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
Cc: Jagan Teki <jteki@openedev.com>
Cc: Pavel Machek <pavel@denx.de>
Cc: Stefan Roese <sr@denx.de>
Cc: Vignesh R <vigneshr@ti.com>