treewide: Remove unused #includes of spi_winbond.h

We want to add some function declarations as static_testable to this
header but including it in a .c file outside of tests will yield a gcc
warning like:

    error: 'function' declared 'static' but never defined
      [-Werror=unused-function]

It seems these includes aren't necessary anyways so we just remove
them.

Change-Id: I17147136579140b94728ceb1c369b1348714bc53
Signed-off-by: Daniel Gröber <dxld@darkboxed.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44090
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Frans Hendriks <fhendriks@eltan.com>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>

src/mainboard/facebook/fbg1701/w25q64.c

@@ -2,7 +2,6 @@
 
 #include <soc/spi.h>
 #include <string.h>
-#include <drivers/spi/spi_winbond.h>
 
 /*
  * SPI VSCC configuration

src/mainboard/portwell/m107/w25q64.c

@@ -2,7 +2,6 @@
 
 #include <soc/spi.h>
 #include <string.h>
-#include <drivers/spi/spi_winbond.h>
 
 /*
  * SPI VSCC configuration