* [bsp][nxp] add missing drv_spi.h
Otherwise when building spi users such as u8g2, gcc will complain can't
find the drv_spi.h.
* [bsp][nxp] enable spi6
* [bsp][nxp] add spi sample code which uses spi6 to loopback
Connect spi6's MISO <--> MSIO, I.E P3_20 and P3_22 with Dupont Line
The sample usage and output would be:
msh >spi_sample
spi rbuf : 0 1 2 3 4 5 6 7 8 9 a b c d e f 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
spi loopback mode test over!
/usr/lib/gcc/arm-none-eabi/13.2.1/../../../arm-none-eabi/bin/ld: rt-thread/bsp/nxp/mcx/mcxn/Libraries/drivers/drv_spi.o: in function `spixfer':
rt-thread/bsp/nxp/mcx/mcxn/Libraries/drivers/drv_spi.c:150:(.text.spixfer+0x102): undefined reference to `LPSPI_MasterTransferEDMA'
/usr/lib/gcc/arm-none-eabi/13.2.1/../../../arm-none-eabi/bin/ld: rt-thread/bsp/nxp/mcx/mcxn/Libraries/drivers/drv_spi.c:160:(.text.spixfer+0x16c): undefined reference to `LPSPI_MasterTransferEDMA'
/usr/lib/gcc/arm-none-eabi/13.2.1/../../../arm-none-eabi/bin/ld: rt-thread/bsp/nxp/mcx/mcxn/Libraries/drivers/drv_spi.o: in function `rt_hw_spi_init':
rt-thread/bsp/nxp/mcx/mcxn/Libraries/drivers/drv_spi.c:211:(.text.rt_hw_spi_init+0x22e): undefined reference to `LPSPI_MasterTransferCreateHandleEDMA'
