Timer Timer:  Timer driver now initializes without complaints.  Need a test driver of some kind to make more testing progress.

Tiva Timer:  Rename tiva_timerlow.c to tiva_timerlow32.c since it only supports 32-bit periodic timers

Tiva Timer:  Allow timeout interrupts even if the reload value is zero.  That is the value that is need to get an interrupt on the wrap from 0xffffffff to 0x00000000

Tiva Timer: Add conditional compilation to enable/disable each timer feature.  Not only does this reduce the footprint by suppressing unused features, it also protects from partially implemented features that are now conditioned on EXPERIMENTAL

Tive Timer:  Add support for ADC trigger generation from one-shot and periodic timers for timeout and match evetns

Tiva Timer: Add support to set the match regiser(s) relative to the timer counter (and prescale) registers.  Enable match interrupts.  These are one time interruprts:  After the match interrupt is dispatched, further match interrupts are disabled

Tive System Control: Add logic to configure the alternatie clock source (ALTCLK).  Needed by the Tiva timer module

STM32 SDIO:  Don't let architectures select CONFIG_MMCSD_SDIOWAIT_WRCOMPLETE unless they have implemented SDIOWAIT_WRCOMPLETE

MMCSD SDIO:  Add support for a new SDWAIT_WRCOMPLETE condition.  The previous logic used a busy-wait loop to pool the card R1 start to determine when the card was ready for the next transfer.  That busy-wait can be quite long -- hundreds of milliseconds.  And alternative is to look the the SD D0 pin which will change state when the card is no longer busy.

This logic implements a change the avoids the busy-wait poll by reconfiguring the SD D0 pin as a GPIO interrupt, then waiting for the card to becom ready without taking up CPU cycles.

This change is conditioned on CONFIG_MMCSD_SDIOWATI_WRCOMPLETE and is currenlty only implemented for the STM32 SDIO driver.

From David Sidrane