use zephyr tincybor instead of mcuboot build-in tinycbor

Zephyr has build-in tinycbor code of version which doesn't
require newlib-c by default. Also the cborattr module is now
taken form the zephyr code.

This patch decrease flash consumption by 10 KB for serial recovery build.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
diff --git a/boot/zephyr/Kconfig b/boot/zephyr/Kconfig
index 7ff8e16..840de9a 100644
--- a/boot/zephyr/Kconfig
+++ b/boot/zephyr/Kconfig
@@ -34,7 +34,7 @@
 	select UART_INTERRUPT_DRIVEN
 	select SERIAL
 	select BASE64
-	select NEWLIB_LIBC
+	select TINYCBOR
 	help
 	  Enable serial recovery feature in mcuboot.