clocksource: move NXP timer selection to drivers/clocksource

clocksource: move NXP timer selection to drivers/clocksource

The Kconfig logic for selecting the scheduler clocksource on
NXP Vybrid (VF610) uses a `choice` block restricted to 32-bit ARM. This
prevents 64-bit architectures, such as the NXP S32 family, from enabling
the NXP Periodic Interrupt Timer (PIT) driver (CONFIG_NXP_PIT_TIMER).

Relocate the NXP clocksource selection from arch/arm/mach-imx/Kconfig to
drivers/clocksource/Kconfig. This allows the configuration to be shared
across different architectures.

Update the selection to include support for ARCH_S32 and add a "None"
option restricted to ARCH_S32, since Vybrid lacks the ARM Architected
Timer. The Vybrid Global Timer option is restricted to ARCH_MULTI_V7
SOC_VF610 platforms to prevent it from being visible on Cortex-M4 builds,
which lack the ARM Global Timer hardware.

Fixes: bee33f22d7c3 ("clocksource/drivers/nxp-pit: Add NXP Automotive s32g2 / s32g3 support")
Signed-off-by: Enric Balletbo i Serra <eballetb@redhat.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@kernel.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260514-fix-nxp-timer-v3-1-a3e68fdb505e@redhat.com