mpir: fix build on ARM Thumb-only platforms

The optimized ARM assembly code is not suitable for Thumb-only
platforms, so use the generic code in such situations.

Fixes:

  http://autobuild.buildroot.net/results/4d7f2a1326f75e11693bdd51ad274079b0dd0ce4/
  (ARM Cortex-M4 toolchain)

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
1 file changed