drm/xe/vsec: fix CONFIG_INTEL_VSEC dependency

drm/xe/vsec: fix CONFIG_INTEL_VSEC dependency

The XE driver can be built with or without VSEC support, but fails to link as
built-in if vsec is in a loadable module:

x86_64-linux-ld: vmlinux.o: in function `xe_vsec_init':
(.text+0x1e83e16): undefined reference to `intel_vsec_register'

The normal fix for this is to add a 'depends on INTEL_VSEC || !INTEL_VSEC',
forcing XE to be a loadable module as well, but that causes a circular
dependency:

        symbol DRM_XE depends on INTEL_VSEC
        symbol INTEL_VSEC depends on X86_PLATFORM_DEVICES
        symbol X86_PLATFORM_DEVICES is selected by DRM_XE

The problem here is selecting a symbol from another subsystem, so change
that as well and rephrase the 'select' into the corresponding dependency.
Since X86_PLATFORM_DEVICES is 'default y', there is no change to
defconfig builds here.

Fixes: 0c45e76fcc62 ("drm/xe/vsec: Support BMG devices")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20250529172355.2395634-2-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
(cherry picked from commit e4931f8be347ec5f19df4d6d33aea37145378c42)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>