misc bring-up fixes

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@2526 42af7a65-404d-4744-a932-0658087f49c3

arch/arm/src/sam3u/sam3u_lowputc.c

@@ -242,7 +242,7 @@ void sam3u_lowsetup(void)
 
   /* Enable clocking for all selected UART/USARTs */
 
-  regval = getreg32(SAM3U_PMC_PCER);
+  regval = 0;
 #ifdef CONFIG_SAM3U_UART
   regval |= (1 << SAM3U_PID_UART);
 #endif