reset: RESET_MCHP_SPARX5 should depend on ARCH_SPARX5

The Microchip Sparx5 switch reset block is only present on Microchip
Sparx5 SoCs.  Hence add a dependency on ARCH_SPARX5, to prevent asking
the user about this driver when configuring a kernel without Sparx5
support.

Fixes: 453ed428

 ("reset: mchp: sparx5: add switch reset driver")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/6e08f6f46123d0712397e901716b48f13fa5dc48.1624627657.git.geert@linux-m68k.org
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>