drivers: uc81xx: Don't produce debug output while waiting
drivers: uc81xx: Don't produce debug output while waiting

The UC81xx driver prints a debug message on every iteration of its
busy wait loop. This makes debug output almost useless. Modify this
code to print a debug message on entry and exit instead.

Signed-off-by: Andreas Sandberg <b15c342f1de186996bcca5e1a23cd684d2fadb32@sandberg.uk>

finikorg/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr