sys: treat epic_stat as opaque

on rust nightly, bindgen adds another brokeness to this struct that
even prevents compiling.
2 jobs for master in 9 minutes and 16 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
failed #7652
firmware

00:00:39

passed #7651
l0dables

00:09:16

 
Name Stage Failure
failed
firmware Build
Cloning into '/builds/astro/rust-card10/card10-sys/firmware/lib/micropython/micropython/lib/berkeley-db-1.xx'...
Cloning into '/builds/astro/rust-card10/card10-sys/firmware/lib/micropython/micropython/lib/libffi'...
Cloning into '/builds/astro/rust-card10/card10-sys/firmware/lib/micropython/micropython/lib/nrfx'...
Cloning into '/builds/astro/rust-card10/card10-sys/firmware/lib/micropython/micropython/lib/stm32lib'...
Cloning into '/builds/astro/rust-card10/card10-sys/firmware/lib/micropython/micropython/lib/mbedtls'...
Submodule path 'card10-sys/firmware/lib/micropython/micropython-lib': checked out 'b89114c8345e15d360c3707493450805c114bc8c'
Failed to recurse into submodule path 'card10-sys/firmware/lib/micropython/micropython'
Failed to recurse into submodule path 'card10-sys/firmware'
ERROR: Job failed: exit code 1