c-periphery: fix SPARC build issue

Some of the serial port highest speed are not defined on SPARC, so
c-periphery should not use them, so we add a patch to fix that.

Fixes:

  http://autobuild.buildroot.net/results/a5d34ef58d45be6fe0b6c8a71ed665d5dc29dfd9/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>