clocksource/drivers/timer-microchip-pit64b: Fix compilation warnings

clocksource/drivers/timer-microchip-pit64b: Fix compilation warnings

Fix the following compilation warnings:
timer-microchip-pit64b.c:68: warning: cannot understand function prototype: 'struct mchp_pit64b_clkevt '
timer-microchip-pit64b.c:82: warning: cannot understand function prototype: 'struct mchp_pit64b_clksrc '
timer-microchip-pit64b.c:283: warning: Function parameter or member 'timer' not described in 'mchp_pit64b_init_mode'
timer-microchip-pit64b.c:283: warning: Function parameter or member 'max_rate' not described in 'mchp_pit64b_init_mode'

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220609094041.1796372-4-claudiu.beznea@microchip.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>