powerpc: Fix typos in Freescale copyright claims

There are many cases that Semiconductor is misspelled.  The patch
fix these typos.

Signed-off-by: Li Yang <leoli@freescale.com>
Acked-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>