ieee802154: `Radio::send` followed by `Radio::recv` panics with v0.14

[japaric]

steps to reproduce

(sorry I did not try to minimize the repro case):

• start from https://github.com/ferrous-systems/embedded-trainings-2020/blob/8b15469bd3d235a7e5c326b9a09cd5ba25022280/beginner/apps/src/bin/radio-recv.rs
• change boards/dk/Cargo.toml to use nrf-hal v0.14.1, cortex-m 0.7.3 and cortex-m-rt 0.7.1
• change beginner/apps/Cargo.toml to use cortex-m 0.7.3 and cortex-m-rt 0.7.1
• from beginner/apps run the radio-recv program

stack backtrace:

stack backtrace:
   0: HardFaultTrampoline
      <exception entry>
   1: lib::inline::__udf
        at ./asm/inline.rs:172:5
   2: __udf
        at ./asm/lib.rs:49:17
   3: cortex_m::asm::udf
        at /home/japaric/.cargo/registry/src/github.com-1ecc6299db9ec823/cortex-m-0.7.3/src/asm.rs:43:5
   4: rust_begin_unwind
        at /home/japaric/github/ferrous-systems/embedded-trainings/common/panic-log/src/lib.rs:12:5
   5: core::panicking::panic_fmt
        at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/panicking.rs:100:14
   6: core::panicking::panic
        at /rustc/f1edd0429582dd29cccacaf50fd134b05593bd9c/library/core/src/panicking.rs:50:5
   7: nrf_hal_common::ieee802154::Radio::state
        at /home/japaric/.cargo/registry/src/github.com-1ecc6299db9ec823/nrf-hal-common-0.14.0/src/ieee802154.rs:665:18
   8: nrf_hal_common::ieee802154::Radio::put_in_rx_mode
        at /home/japaric/.cargo/registry/src/github.com-1ecc6299db9ec823/nrf-hal-common-0.14.0/src/ieee802154.rs:626:21
   9: nrf_hal_common::ieee802154::Radio::start_recv
        at /home/japaric/.cargo/registry/src/github.com-1ecc6299db9ec823/nrf-hal-common-0.14.0/src/ieee802154.rs:397:9
  10: nrf_hal_common::ieee802154::Radio::recv_timeout
        at /home/japaric/.cargo/registry/src/github.com-1ecc6299db9ec823/nrf-hal-common-0.14.0/src/ieee802154.rs:355:13
  11: radio_recv::__cortex_m_rt_main
        at src/bin/radio-recv.rs:36:15
  12: main
        at src/bin/radio-recv.rs:13:1
  13: Reset
(HOST) ERROR the program panicked

---

hal v0.13.0 works fine. I'm currently investigating the cause

[japaric]

after PR #356 a send operation leaves the radio in the TXDISABLED state (instead of TXIDLE). recv is lacking the logic to handle starting from that state so it panics. looking into adding code to handle that case