mailbox: tegra: relax TEGRA_HSP_MBOX Kconfig dependencies

With the addition of the ARCH_TEGRA_194_SOC driver, we get a new Kconfig warning:

warning: (ARCH_TEGRA_186_SOC && ARCH_TEGRA_194_SOC) selects TEGRA_HSP_MBOX which has unmet direct dependencies (MAILBOX && ARCH_TEGRA_186_SOC)

It looks like the dependency is a bit too strict here, allowing the driver to
be built for any Tegra chip avoids the problem.

Fixes: 6f9ed07f ("soc/tegra: Add Tegra194 SoC configuration option")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>