timer: Add generic udelay() implementation

Add GENERIC_UDELAY Kconfig option so that a generic
udelay() implementation is provided utilizing the
monotonic timer. That way each board/chipset doesn't
need to duplicate the same udelay(). Additionally,
assume that GENERIC_UDELAY implies init_timer()
is not required.

BUG=None
BRANCH=None
TEST=Built nyan, ryu, and rambi. May need help testing.

Change-Id: I7f511a2324b5aa5d1b2959f4519be85a6a7360e8
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 1a85fbcad778933d13eaef545135abe7e4de46ed
Original-Change-Id: Idd26de19eefc91ee3b0ceddfb1bc2152e19fd8ab
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/219719
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/9334
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/src/soc/rockchip/rk3288/Kconfig b/src/soc/rockchip/rk3288/Kconfig
index 0865fe8..70951a5 100644
--- a/src/soc/rockchip/rk3288/Kconfig
+++ b/src/soc/rockchip/rk3288/Kconfig
@@ -26,6 +26,7 @@
 	select ARCH_RAMSTAGE_ARMV7
 	select CPU_HAS_BOOTBLOCK_INIT
 	select HAVE_MONOTONIC_TIMER
+	select GENERIC_UDELAY
 	select HAVE_UART_MEMORY_MAPPED
 	select HAVE_UART_SPECIAL
 	select BOOTBLOCK_CONSOLE