mb/lenvovo/*: Clean mainboard.c and devicetree

* Move board specific SPI registers to devicetree
* Remove unused headers
* Remove obsolete methods
* Fix coding style
* Fix Thinkpad L520 SPI lvscc register

Except for Thinkpad L520, no functional change has been done,
just moving stuff around.

Change-Id: I692a5632030fe2fedbe9a90f86251000f1360fb2
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/19494
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/src/mainboard/lenovo/t520/devicetree.cb b/src/mainboard/lenovo/t520/devicetree.cb
index 6c638e5..0065799 100644
--- a/src/mainboard/lenovo/t520/devicetree.cb
+++ b/src/mainboard/lenovo/t520/devicetree.cb
@@ -72,6 +72,9 @@
 
 			register "pcie_hotplug_map" = "{ 0, 0, 0, 1, 0, 0, 0, 0 }"
 
+			register "spi_uvscc" = "0x2005"
+			register "spi_lvscc" = "0x2005"
+
 			device pci 16.0 on end # Management Engine Interface 1
 			device pci 16.1 off end
 			device pci 16.2 off end