drivers: spi: eliminate dead code in spi_mcux_lpspi

The `spi_mcux_transceive` had 2 return calls when the
`CONFIG_SPI_MCUX_LPSPI_DMA` flag was active. The first return would be
called and the later was unreachable. With the fix, now the return calls
are mutually exclusive. Also, the `transceive` call is not compiled with
the `CONFIG_SPI_MCUX_LPSPI_DMA` flag is active.
Fixes #59533

Signed-off-by: Dipak Shetty <dipak.shetty@zeiss.com>