Improve the jerry port api documents. (#4977)

Notable changes:
  - Remove the comments in port impl, that's easily getting to in-consistence
  - Sync the jerryscript-port.h and 05.PORT-API.md
  - Fixes the invalid comment in port codes

JerryScript-DCO-1.0-Signed-off-by: Yonggang Luo luoyonggang@gmail.com

targets/os/nuttx/jerry-port.c

@@ -19,23 +19,12 @@
 
 #include "jerryscript-port.h"
 
-/**
- * Default implementation of jerry_port_log. Prints log messages to stderr.
- */
 void
-jerry_port_log (const char *message_p) /**< message */
+jerry_port_log (const char *message_p)
 {
   (void) message_p;
 } /* jerry_port_log */
 
-/**
- * Read a line from standard input as a zero-terminated string.
- *
- * @param out_size_p: length of the string
- *
- * @return pointer to the buffer storing the string,
- *         or NULL if end of input
- */
 jerry_char_t *
 jerry_port_line_read (jerry_size_t *out_size_p)
 {
@@ -43,20 +32,12 @@ jerry_port_line_read (jerry_size_t *out_size_p)
   return NULL;
 } /* jerry_port_line_read */
 
-/**
- * Aborts the program.
- */
 void
 jerry_port_fatal (jerry_fatal_code_t code)
 {
   exit ((int) code);
 } /* jerry_port_fatal */
 
-/**
- * Dummy function to get the time zone adjustment.
- *
- * @return 0
- */
 int32_t
 jerry_port_local_tza (double unix_ms)
 {
@@ -66,11 +47,6 @@ jerry_port_local_tza (double unix_ms)
   return 0;
 } /* jerry_port_local_tza */
 
-/**
- * Dummy function to get the current time.
- *
- * @return 0
- */
 double
 jerry_port_current_time (void)
 {