net: coap: Rename ZOAP library

ZOAP library has certain limitations in parsing and preparation of
coap messages. It can handle only on single network fragment. If
network packet is split between multiple fragments it fails. This
patch is just copy and rename of 'zoap' to 'coap'.

Signed-off-by: Ravi kumar Veeramally <ravikumar.veeramally@linux.intel.com>
diff --git a/doc/zephyr.doxyfile b/doc/zephyr.doxyfile
index a135882..03a5597 100644
--- a/doc/zephyr.doxyfile
+++ b/doc/zephyr.doxyfile
@@ -107,7 +107,7 @@
 			../include/arch/arm/cortex_m \
                         ../include/arch/nios2/ \
                         ../lib/libc/minimal/include/ \
-                        ../include/net/zoap.h \
+                        ../include/net/coap.h \
                         ../include/net/dns_resolve.h \
                         ../tests/ztest/include/
 INPUT_ENCODING         = UTF-8