Add missing volatile to status flags to prevent "infinite" loop after optimization

[TheSlowGrowth]

To prevent the while loops from being optimized into very long loops.

Without this change, loops such as this one in SD_read() (sd_diskio.c:154) get "optimized" into 30s loops, when the (ReadStatus == 0) check gets optimized out:

        while((ReadStatus == 0) && ((HAL_GetTick() - timeout) < SD_TIMEOUT)) {}

This can be observed with arm-gcc-none-eabi 10 2021-q4-major using DaisyProject.cmake
This makes the SD unusable.

[github-actions]

Test Results

150 tests  ±0   150 ✅ ±0   0s ⏱️ ±0s
  1 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit e8a01a3. ± Comparison against base commit ea7f924.

♻️ This comment has been updated with latest results.

[stephenhensley]

Woah, fascinating.

I've hit this loop a few times before, but never reliably.
I have almost entirely used the Make builds, so maybe some flag set there causes this to be more intermittent than with the CMake build.

In either case, nice catch. Thanks for the update!
I'll give this a quick test before the end of the week, and get it merged!