Revert "posix: device_io: mark pwrite() buf as const"

This reverts commit c14f97f194.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

lib/posix/options/device_io.c

@@ -99,7 +99,7 @@ int pselect(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
 	return zvfs_select(nfds, readfds, writefds, exceptfds, timeout, sigmask);
 }
 
-ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset)
+ssize_t pwrite(int fd, void *buf, size_t count, off_t offset)
 {
 	size_t off = (size_t)offset;