platform/x86: dell-smbios: Resolve dependency error on DCDBAS

When the DELL_SMBIOS_SMM backend is enabled, the DELL_SMBIOS symbol
depends on DELL_DCDBAS, and we must avoid the situation where
DELL_SMBIOS=y and DCDBAS=m.

Adding the conditional dependency to DELL_SMBIOS such as:

depends !DELL_SMBIOS_SMM || (DCDBAS || DCDBAS=n)

results in the Kconfig tooling complaining about a circular dependency,
although it appears to work in practice.

Avoid the errors by simplifying the dependency and forcing DELL_SMBIOS
to be <= DCDBAS if DCDBAS is enabled (thanks to Greg KH for the
suggestion).

Cc: Mario.Limonciello@dell.com
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>