event/cnxk: add external clock support for timer

event/cnxk: add external clock support for timer

Add external clock support for cnxk timer adapter.

External clock mapping is as follows:
RTE_EVENT_TIMER_ADAPTER_EXT_CLK0 = TIM_CLK_SRC_10NS,
RTE_EVENT_TIMER_ADAPTER_EXT_CLK1 = TIM_CLK_SRC_GPIO,
RTE_EVENT_TIMER_ADAPTER_EXT_CLK2 = TIM_CLK_SRC_PTP,
RTE_EVENT_TIMER_ADAPTER_EXT_CLK3 = TIM_CLK_SRC_SYNCE,

TIM supports clock input from external GPIO, PTP, SYNCE clocks.
Input resolution is adjusted based on CNTVCT frequency for better
estimation.

Since TIM is unaware of input clock frequency, application is
expected to pass the frequency.
Example:
	-a 0002:0e:00.0,tim_eclk_freq=122880000-0-0

The order of frequencies above is GPIO-PTP-SYNCE.

Signed-off-by: Shijith Thotton <sthotton@marvell.com>
Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>