stm32f429i_disc1_stm32cube: Update variable names
stm32f429i_disc1_stm32cube: Update variable names

Corrects variables in the stm32f429i_disc1_stm32cube target's FreeRTOS
hooks to use the appropriately named TCBs/stacks.

Change-Id: I4bfa1e6460903c88960655409cc94e0cdf94a70d
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/84123
Pigweed-Auto-Submit: Armando Montanez <97ef6fdb231c129ac8827d9f0c4106bfbf57f74f@google.com>
Reviewed-by: Carlos Chinchilla <cdf38d65522bb1d68fb5b958430f926735c310be@google.com>
Commit-Queue: Auto-Submit <14637eda5603879df170705285bf30f5996692f0@pigweed.google.com.iam.gserviceaccount.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed