clocksource/drivers/h8300_timer8: Separate the Kconfig option from the arch

The current Kconfig option is the H8300 arch option. In order to comply to the
current rule, let's create a specific option for the timer8 and select it
from the arch's Kconfig.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 56bd16e..dc2b899 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -60,7 +60,7 @@
 obj-$(CONFIG_CLKSRC_TANGO_XTAL)		+= tango_xtal.o
 obj-$(CONFIG_CLKSRC_IMX_GPT)		+= timer-imx-gpt.o
 obj-$(CONFIG_ASM9260_TIMER)		+= asm9260_timer.o
-obj-$(CONFIG_H8300)			+= h8300_timer8.o
+obj-$(CONFIG_H8300_TMR8)		+= h8300_timer8.o
 obj-$(CONFIG_H8300_TMR16)		+= h8300_timer16.o
 obj-$(CONFIG_H8300_TPU)			+= h8300_tpu.o
 obj-$(CONFIG_CLKSRC_ST_LPC)		+= clksrc_st_lpc.o