This commit adds APIs to initialize and configure the LP ADC from the HP
core and also adds APIs to read the raw and converted ADC values from the LP core.
Previously we would calculate the wakeup ticks upon every wakeup using the lp-timer clock frequency,
but this caused the binary to pull in software division functions, increasing the binary size.
This value is now precalculated by the hp-core when we configure the ULP. This saves about 1k bytes.
