drivers: uart_nrfx_uarte: Remove redundant HW_RX_COUNTING_ENABLED calls
drivers: uart_nrfx_uarte: Remove redundant HW_RX_COUNTING_ENABLED calls

Merge three adjacent `if (HW_RX_COUNTING_ENABLED(data))` blocks into
a common one.

Signed-off-by: Andrzej Głąbek <6788b8d556a8a447102338fc996c42180ecff44e@nordicsemi.no>

zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr