storm: Initialize clock, pinmux for NAND if present on board

This patch runs basic NAND initialization code on Proto 0.2 boards which
have been reworked for NAND. It makes sense to do this in coreboot for
two reasons:
- In general, it is reasonable for coreboot to initialize clocks and such
  in preparation for depthcharge's use. Waiting times can be pooled, and
  the initialization itself here is very fast.
- There is a kernel bug which requires that the clock is already initialized
  before the kernel loads NAND support. coreboot is a more sensible place
  to put a workaround than depthcharge because depthcharge initializes
  things lazily, but when booting from USB, depthcharge won't need to look
  at NAND.
This change involves bringing in an additional header file, ebi2.h, from U-Boot.

TEST=Booted a kernel from USB and verified that NAND came up without any
depthcharge hacks, whereas previously a USB-booted kernel would be unable
to access NAND even with the same drivers compiled in due to an initialization
failure.
BUG=chromium:403432
BRANCH=none

Change-Id: I04e99cb39d16848a6ed75fe0229b8f79bdf2e035
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 9be29da5ccad9982f146ae00344f30598ef2371c
Original-Signed-off-by: Dan Ehrenberg <dehrenberg@chromium.org>
Original-Change-Id: I1760ecb4e47438311d80e34326e45578c608481c
Original-Reviewed-on: https://chromium-review.googlesource.com/225277
Original-Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: http://review.coreboot.org/9402
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
diff --git a/src/mainboard/google/storm/mainboard.c b/src/mainboard/google/storm/mainboard.c
index 59e7ce7..094eaef 100644
--- a/src/mainboard/google/storm/mainboard.c
+++ b/src/mainboard/google/storm/mainboard.c
@@ -114,6 +114,8 @@
 	 setup_usb();
 	 deassert_sw_reset();
 	 setup_tpm();
+	 /* Functionally a 0-cost no-op if NAND is not present */
+	 board_nand_init();
 }
 
 static void mainboard_enable(device_t dev)