Change include style to use system includes

The libcper header files in `libcper` are installed to
`usr/include/libcper`. Use that system includes in `libcper` source
instead of using the project includes.

Change-Id: I596edc2c754dae4829844f535a1e34caa246fb43
Signed-off-by: Thu Nguyen <thu@os.amperecomputing.com>
diff --git a/generator/cper-generate.c b/generator/cper-generate.c
index 58f14a3..91eaf41 100644
--- a/generator/cper-generate.c
+++ b/generator/cper-generate.c
@@ -7,10 +7,10 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include "Cper.h"
-#include "gen-utils.h"
-#include "sections/gen-section.h"
-#include "cper-generate.h"
+#include <libcper/Cper.h>
+#include <libcper/generator/gen-utils.h>
+#include <libcper/generator/sections/gen-section.h>
+#include <libcper/generator/cper-generate.h>
 
 EFI_ERROR_SECTION_DESCRIPTOR *generate_section_descriptor(char *type,
 							  const size_t *lengths,