ARM: OMAP: Make OMAP clocksource source selection runtime

Current OMAP code supports couple of clocksource options based on compilation flag (CONFIG_OMAP_32K_TIMER). The 32KHz sync-timer and a gptimer which can run on 32KHz or system clock (e.g 38.4 MHz)

This patch series cleans up the existing 32k-sync timer implementation without any major code changes, uses kernel parameter to override the default clocksource of "counter_32k", also in order to support some OMAP based derivative SoCs like AM33XX which doesn't have 32K sync-timer hardware IP, adds hwmod lookup for omap2+ devices, and if lookup fails then fall back to gp-timer.

if(use_gptimer_clksrc == true)
? ? ? ?gptimer clocksource init;
else if (counter_32 init == false)
? ? ? ?/* Fallback to gptimer */
? ? ? ?gptimer clocksource init(;

With this, we should be able to support multi-omap boot including devices with/without 32k-sync timer.

This patch-series has been boot tested on AM37xEVM platform, it would be helpful if somebody help me to validate it on OMAP1/2 platforms.

The patches are also available at -
https://github.com/hvaibhav/am335x-linux ? 32ksync-timer-cleanup

History:
========
Changes from V3:
http://www.mail-archive.com/linux-omap at vger.kernel.org/msg66462.html ? ? ? ?- Fixed all review comments from Kevin H
? ? ? ? ? ? ? ?* Moved counter_32k CR register offset handling to ? ? ? ? ? ? ? ? ?counter_32k.c file, so now, calling funtion don't have ? ? ? ? ? ? ? ? ?to maintain or add offset to base addr.
? ? ? ? ? ? ? ?* Added comment for funtion omap_init_clocksource_32k() ? ? ? ? ? ? ? ?* Used resource_size() for calculate size
? ? ? ? ? ? ? ?* Convert WARN_ON to pr_warn