x86-generic: enable CONFIG_DMIID

This shouldn't affect compatiblity with kernel modules and will allow us to
find out under which hypervisor we're running.

targets/x86-generic/kernel-config

@@ -3964,7 +3964,7 @@ CONFIG_IIO_CONSUMERS_PER_TRIGGER=2
 CONFIG_FIRMWARE_MEMMAP=y
 # CONFIG_DELL_RBU is not set
 # CONFIG_DCDBAS is not set
-# CONFIG_DMIID is not set
+CONFIG_DMIID=y
 # CONFIG_DMI_SYSFS is not set
 # CONFIG_ISCSI_IBFT_FIND is not set
 # CONFIG_GOOGLE_FIRMWARE is not set