drivers/firmware/dmi_scan.c: make dmi_name_in_vendors more focused

drivers/firmware/dmi_scan.c: make dmi_name_in_vendors more focused

The current implementation of dmi_name_in_vendors() is an invitation to
lazy coding and false positives [1].  Searching for a string in 8 know
what you're looking for, so you should know where to look.  strstr isn't
fast, especially when it fails, so we should avoid calling it when it just
can't succeed.

Looking at the current users of the function, it seems clear to me that
they are looking for a system or board vendor name, so let's limit
dmi_name_in_vendors to these two DMI fields.  This much better matches the
function name, BTW.

[1] We currently have code looking for short names in DMI data, such
as "IBM", "ASUS" or "Acer". I let you guess what will happen the day
other vendors ship products named, for example, "SCHREIBMEISTER",
"PEGASUS" or "Acerola".

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>