clocksource/drivers/exynos_mct: Remove mct interrupt index enum

clocksource/drivers/exynos_mct: Remove mct interrupt index enum

MCT driver define an enum which list global and local timer's
irq index. Most of them are not used but MCT_G0_IRQ and
MCT_L0_IRQ and these two are at a fixed offset/index.
Get rid of this enum and use a #define for the used irq index.

No functional changes expected.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Link: https://lore.kernel.org/r/20220221174547.26176-1-alim.akhtar@samsung.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>