clocksource/drivers/timer-tegra186: Avoid 64-bit divide operation

clocksource/drivers/timer-tegra186: Avoid 64-bit divide operation

Building the driver on xtensa fails with

tensa-linux-ld: drivers/clocksource/timer-tegra186.o:
	in function `tegra186_timer_remove':
timer-tegra186.c:(.text+0x350):
	undefined reference to `__udivdi3'

Avoid the problem by rearranging the offending code to avoid the 64-bit
divide operation.

Fixes: 28c842c8b0f5 ("clocksource/drivers/timer-tegra186: Add WDIOC_GETTIMELEFT support")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Cc: Pohsun Su <pohsuns@nvidia.com>
Cc: Robert Lin <robelin@nvidia.com>
Link: https://lore.kernel.org/r/20250614175556.922159-1-linux@roeck-us.net