driver/spi: STM32 Revert while loop on tx only

This commit reverted while loop on tx only.
This commit solves SPI loopback failure and SPI wrong behaviour on RX.
fix:
* zephyrproject-rtos/zephyr#35297
* zephyrproject-rtos/zephyr#35539

Revert "drivers/spi: STM32: This solves SPI infinite loop on Tranceive"

This reverts commit 50c2acbc03e7a48a09880b6fcb8c22256bffa70c.

Signed-off-by: Affrin Pinhero <affrin.pinhero@hcl.com>