plat/arm: Use common build flag for using generic sp804 driver

SP804 TIMER is not platform specific, and current code base adds
multiple defines to use this driver. Like FVP_USE_SP804_TIMER and
FVP_VE_USE_SP804_TIMER.

This patch removes platform specific build flag and adds generic
flag `USE_SP804_TIMER` to be set to 1 by platform if needed.

Change-Id: I5ab792c189885fd1b98ddd187f3a38ebdd0baba2
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
diff --git a/plat/arm/board/fvp_ve/fvp_ve_bl2_setup.c b/plat/arm/board/fvp_ve/fvp_ve_bl2_setup.c
index 25e0964..4ccae27 100644
--- a/plat/arm/board/fvp_ve/fvp_ve_bl2_setup.c
+++ b/plat/arm/board/fvp_ve/fvp_ve_bl2_setup.c
@@ -25,7 +25,7 @@
 {
 	arm_bl2_platform_setup();
 
-#ifdef FVP_VE_USE_SP804_TIMER
+#if USE_SP804_TIMER
 	/*
 	 * Enable the clock override for SP804 timer 0, which means that no
 	 * clock dividers are applied and the raw (35 MHz) clock will be used
@@ -37,5 +37,5 @@
 			SP804_TIMER_CLKMULT, SP804_TIMER_CLKDIV);
 #else
 	generic_delay_timer_init();
-#endif /* FVP_VE_USE_SP804_TIMER */
+#endif /* USE_SP804_TIMER */
 }