Build: Ensure all *.patch files use Unix style.

- Git patch files are text files
- The line endings of the patches follow the Unix style, using LF (Line Feed).

The same attributes can already be found in TF-M:
43187bc2d4a8c0549a331167a3b8931db8bfcb01

Change-Id: Icd5422931fb1f01b3919f2e5d7f43acb874a71bc
Signed-off-by: David Vincze <david.vincze@arm.com>
diff --git a/.gitattributes b/.gitattributes
index 6a3a768..cd87feb 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,5 +1,9 @@
 * text=auto
 
+# Explicitly declare text files to make sure possible local wrong config
+# of git does not override them on checkout
+*.patch text eol=lf
+
 # Text files that should be normalized
 *.c text
 *.h text