gcc: config: microblaze: fix cpu version check

gcc: config: microblaze: fix cpu version check

The MICROBLAZE_VERSION_COMPARE was incorrectly using strcasecmp
instead of strverscmp to check the mcpu version against feature
options.  By simply changing the define to use strverscmp,
the new version 10.0 is treated correctly as a higher version
than previous versions.

Fix incorrect warning with -mcpu=10.0:
  warning: '-mxl-multiply-high' can be used only with
  '-mcpu=v6.00.a' or greater

Signed-off-by: Neal Frager <neal.frager@amd.com>
Signed-off-by: Michael J. Eager <eager@eagercon.com>