Clean up error handling

core/os/os_freebsd.odin

@@ -438,7 +438,7 @@ close :: proc(fd: Handle) -> Errno {
 	if result == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 // If you read or write more than `INT_MAX` bytes, FreeBSD returns `EINVAL`.
@@ -495,7 +495,7 @@ rename :: proc(old_path, new_path: string) -> Errno {
 	if res == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 remove :: proc(path: string) -> Errno {
@@ -505,7 +505,7 @@ remove :: proc(path: string) -> Errno {
 	if res == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 make_directory :: proc(path: string, mode: mode_t = 0o775) -> Errno {
@@ -515,7 +515,7 @@ make_directory :: proc(path: string, mode: mode_t = 0o775) -> Errno {
 	if res == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 remove_directory :: proc(path: string) -> Errno {
@@ -525,7 +525,7 @@ remove_directory :: proc(path: string) -> Errno {
 	if res == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 is_file_handle :: proc(fd: Handle) -> bool {
@@ -654,7 +654,7 @@ _closedir :: proc(dirp: Dir) -> Errno {
 	if rc != 0 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 @private
@@ -803,7 +803,7 @@ set_current_directory :: proc(path: string) -> (err: Errno) {
 	if res == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 exit :: proc "contextless" (code: int) -> ! {