kernel: tests: Increased TX/RX buf size in pipe test
kernel: tests: Increased TX/RX buf size in pipe test

Increased TX/RX buffer size by one in pipe test to prevent buffer
overrun.

Some test will transfer one byte more then the number of bytes
supported by the pipe, in case the buffer size is the same as the
size of the pipe this will result in a buffer overrun.
Tools such as address sanitizer would detect this overrun and fail the
test.

Signed-off-by: Jan Van Winkel <d648848808a4d751aff880668aa63d2d9d94a5a4@dxplore.eu>

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