code was allocating a semaphore handle on every write access.

Every time frequency was changed, an additional cpu frequency change callback was added. Code now adds ONE callback and uses a static variable to denote active channels requiring timer reconfig on base frequency change.

Change apbChangeCallback to double link list, roll cpu freq change newest->oldest then Oldest->Newest to minimize UART disruption.
Fix duplicate addApbChangeCallback detection.
Fix UART MUTEX deadlock when log_x calls occuring from apbCallbacks

Fix incorrect error message. If timer clock source was REF_CLK, (slow speed 8mhz) ApbClockChange callback was incorrectly reporting that timer channel was inactive.