mtd: hyperbus: HBMC_AM654 should depend on ARCH_K3

The AM65x HyperBus controller is only present on Texas Instruments AM65x
SoCs.  Hence add a dependency on ARCH_K3, to prevent asking the user
about this driver when configuring a kernel without support for the
Texas Instruments Inc. K3 multicore SoC architecture.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/9fd6b975adba710158f28aa603cf87a6d189a418.1646655894.git.geert+renesas@glider.be