soc: ti: fix irq-ti-sci link error

The irqchip driver depends on the SoC specific driver, but we want
to be able to compile-test it elsewhere:

WARNING: unmet direct dependencies detected for TI_SCI_INTA_MSI_DOMAIN
  Depends on [n]: SOC_TI [=n]
  Selected by [y]:
  - TI_SCI_INTA_IRQCHIP [=y] && TI_SCI_PROTOCOL [=y]

drivers/irqchip/irq-ti-sci-inta.o: In function `ti_sci_inta_irq_domain_probe':
irq-ti-sci-inta.c:(.text+0x204): undefined reference to `ti_sci_inta_msi_create_irq_domain'

Rearrange the Kconfig and Makefile so we build the soc driver whenever
its users are there, regardless of the SOC_TI option.

Fixes: 49b32315 ("soc: ti: Add MSI domain bus support for Interrupt Aggregator")
Fixes: f011df61 ("irqchip/ti-sci-inta: Add msi domain support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Olof Johansson <olof@lixom.net>