Temporarily use u-boot build with regulator change reverted

This change caused i2c timeouts on the BraveHeart's touchscreen.

https://github.com/crust-firmware/arm-trusted-firmware/commit/6e19a238bc4743964029a8ff36b878d3295e7a28
1 job for master in 1 minute and 6 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #622273574
build

00:01:06