spelling: s/retreive/retrieve/

Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 4283fa3..ae2e2a3 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -632,7 +632,7 @@
 }
 
 /*
- * Call early during boot, before mem init or bootmem, to retreive the RTAS
+ * Call early during boot, before mem init or bootmem, to retrieve the RTAS
  * informations from the device-tree and allocate the RMO buffer for userland
  * accesses.
  */