at91sam9/at91cap: improve clock framework

calculate dynamically the clock rate and pllb setting for usb

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/cpu/arm926ejs/at91/Makefile b/cpu/arm926ejs/at91/Makefile
index 34e7461..3d45c42 100644
--- a/cpu/arm926ejs/at91/Makefile
+++ b/cpu/arm926ejs/at91/Makefile
@@ -55,6 +55,8 @@
 COBJS-$(CONFIG_HAS_DATAFLASH)	+= at91sam9rl_spi.o
 endif
 COBJS-$(CONFIG_AT91_LED)	+= led.o
+COBJS-y += clock.o
+COBJS-y += cpu.o
 COBJS-y	+= timer.o
 SOBJS	= lowlevel_init.o