Detects whether we are running as a VMware guest or not. Detection is
based upon DMI vendor string.
It provides a function:
int is_vmware_guest(void)
that can be used easily to detect if we are running as a VMware guest
or not.
I haven't used PCI vendor Id since that requires copying a trunk of
codes from early_quirks() and I think copying code is not good. And
reusing codes from early_quirks() needs intrivial change to present
codes structure. Comparatively, checking "VMware" string against DMI
manufacturer is a lot more simpler (one-line code). Also there's no
evidence indicating that VMware will change their vendor string in
near future. Therefore I choose to use simpler way.
Tested on x86 and x86-64 VMs and machines.