fmu-v6xrt lpuart singlewire for RC telemetry

[PetervdPerk-NXP]

Updates IMXRT driver to support RC telemetry.

Also changes rc_input singlewire mode to pushpull for better signalling.

Pending on PX4/NuttX#307

[davids5]

Pending on PX4/NuttX#307 - is merged - please repoint this PR

[dk7xe]

nsh: sysinit: fopen failed: No such file or directory

NuttShell (NSH) NuttX-11.0.0
nsh> ver all
HW arch: PX4_FMU_V6XRT
HW type: V6XRT
HW FMUM ID: 0x000
HW BASE ID: 0x003
PX4 git-hash: bbaed84
PX4 version: 1.15.0 80 (17760384)
PX4 git-branch: pr-lpuart-singlewire-v6xrt
OS: NuttX
OS version: Release 11.0.0 (184549631)
OS git-hash: f8b59abbf98e19a184114c3f54462810ed5990ab
Build datetime: May 25 2024 20:58:17
Build uri: localhost
Build variant: default
Toolchain: GNU GCC, 9.3.1 20200408 (release)
PX4GUID: 00090000000000000000829297441d1a180e
MCU: i.MX RT1170 rB0, rev. 0
nsh>

nsh> rc_input status
INFO [rc_input] Max update rate: 250 Hz
INFO [rc_input] UART device: /dev/ttyS4
INFO [rc_input] UART RX bytes: 270691
INFO [rc_input] RC state: searching for signal: GHST
rc_input: cycle time: 30492 events, 621143us elapsed, 20.37us avg, min 6us max 870us 30.530us rms
rc_input: publish interval: 18790 events, 4096.65us avg, min 1785us max 15986us 680.536us rms
nsh>

@PetervdPerk-NXP but no telemetry on my Tandem X20S other than from the Ghost Module itself.
On my racers with FETtec FC i do get telemetry

[dk7xe]

After switching the GHST protocol from Race250 to Normal telemetry works

Switched back to Race250 protocol.
Now telemetry works as well after rebinding the Ghost Atto Duo RX

[dk7xe]

To me it looks like this is good to go

[PetervdPerk-NXP]

Pending on testing on Pixhawk 4 - FMUv5 due to SER_SINGLEWIRE_PUSHPULL change.
@dk7xe you happen to have a Pixhawk 4?

See #23216

[PetervdPerk-NXP]

Dropped SER_SINGLEWIRE_PUSHPULL change it's working fine without it.
Made a seperate PR for that see #23216

@davids5 can we merge this?