mindtct: Check for multiplication overflow in alloc_power_stats()

Assert if any of the multiplications, which are then used to allocate
memory, would overflow.

Closes: #91
2 jobs for <span class="ref-name">wip/hadess/nbis-mul-check</span> in 6 minutes and 3 seconds (queued for 17 seconds)
Status Job ID Name Coverage
  Build
passed #62525
build

00:03:08

 
  Test
passed #62526
flatpak master

00:02:55