posix: sys/stat.h: move O_ACCMODE, RD WRONLY, RDWR to fcntl.h

Previously, `<sys/stat.h>` was declaring the following constants
which should be declared in `<fcntl.h>` according to POSIX.

Signed-off-by: Chris Friedt <[email protected]>

Author: cfriedt

include/zephyr/posix/fcntl.h

@@ -13,6 +13,12 @@
 #define O_CREAT 0x0200
 #endif
 
+#define O_ACCMODE (O_RDONLY | O_WRONLY | O_RDWR)
+
+#define O_RDONLY 00
+#define O_WRONLY 01
+#define O_RDWR	 02
+
 #define O_APPEND   0x0400
 #define O_EXCL	   0x0800
 #define O_NONBLOCK 0x4000