zephyr: boot_serial: fix CRC header warning

The crc16.h header has been deprecated in Zephyr.
Update include directive to use the new header.

Signed-off-by: Emanuele Di Santo <emdi@nordicsemi.no>
diff --git a/boot/boot_serial/src/boot_serial.c b/boot/boot_serial/src/boot_serial.c
index 449a979..bf1474e 100644
--- a/boot/boot_serial/src/boot_serial.c
+++ b/boot/boot_serial/src/boot_serial.c
@@ -31,7 +31,7 @@
 #include <misc/byteorder.h>
 #include <misc/__assert.h>
 #include <flash.h>
-#include <crc16.h>
+#include <crc.h>
 #include <base64.h>
 #include <cbor.h>
 #else