openblas: drop SSE_GENERIC target

Fixes #10856

The SSE_GENERIC target fails to build with a "sgemm_kernel.o: No such file
or directory" error. Several upstream bug reports exist for this:

https://github.com/xianyi/OpenBLAS/issues/502
https://github.com/xianyi/OpenBLAS/issues/685

In both cases, upstream suggests using a different target definition
instead.  E.G.  from issue 685:

You may use NORTHWOOD on x86: make TARGET=NORTHWOOD that uses SSE2
instructions.  It's very hard to find non-SSE2 x86 CPUs today.  For x86-64
use the PRESCOTT target

So drop the SSE_GENERIC target.  The only x86_64 variant we support not
covered by a more specific openblas target is the default variant, nocona
and jaguar.

Nocona was a Xeon variant of the P4 "Prescott" architecture, so use the
PRESCOTT openblas target:

https://en.wikipedia.org/wiki/Xeon#Nocona_and_Irwindale

Jaguar is from the Bobcat family, so use the BOBCAT openblas target:

https://en.wikipedia.org/wiki/List_of_AMD_microprocessors#Bobcat_core_architecture_(APU)



[Peter: add Jaguar as pointed out by Arnout]
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>