SPI (test) is not working for LPCXpresso54114

[Tobi0610]

Describe the bug
SPI (test) is not working for LPCXpresso54114.
I created my own SPI-Master sample project and tried also the spi-test in zephyrproject/zephyr/tests/drivers/spi/spi_loopback/. Both are not working for LPCXpresso54114.
The spi-loopback-test (for LPCXpresso54114) was broken by 22326f6

To Reproduce
Steps to reproduce the behavior:

1. hand wire MOSI and MISO of SPI_5 (Arduino_Header) of LPCXpresso54114 together
2. run test zephyrproject/zephyr/tests/drivers/spi/spi_loopback/ for LPCXpresso54114

Expected behavior
Test should pass

Impact
Not able to use SPI with LPCXpresso54114.

Screenshots or console output
Console output of SPI test execution:

Running test suite test_spi
===================================================================
starting test - test_spi_loopback
I: SPI test on buffers TX/RX 0x200016ec/0x20000408
I: Start
I: CS control inhibited (no GPIO device)
I: Passed
I: Start
E: Rx Buffer should contain NOP frames but got: 0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,    Assertion failed at CMAKE_SOURCE_DIR/src/spi.c:192: spi_null_tx_buf: (1 is true)
Buffer not as expected
FAIL - test_spi_loopback
===================================================================
Test suite test_spi failed.
===================================================================
PROJECT EXECUTION FAILED    Assertion failed at CMAKE_SOURCE_DIR/src/spi.c:399: spi_async_call_cb: (ret is true)
one or more events are not ready

Environment:

• OS: Linux Manjaro (ARCH)
• Toolchain: Zephyr SDK
• branch: master

Additional context