bus: bt1-axi: Optimize the return points in the driver

It's better to have a single return statement where it's applicable
instead of returning from a conditional statement if-clause. Let's
do this in the request registers, clock and IRQ methods.

Link: https://lore.kernel.org/r/20200528145050.5203-5-Sergey.Semin@baikalelectronics.ru


Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Olof Johansson <olof@lixom.net>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: soc@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>