The below Stored Procedure searches within all the stored procedures in the SQL server database, views, and functions for the given function name. This stored procedure also search for any text written in the stored procedure, not just function names.
CREATE PROCEDURE dbo.Find_Text
@SearchValue nvarchar(500)
AS
SELECT DISTINCT
s.name+'.'+o.name AS Object_Name,o.type_desc
FROM sys.sql_modules m
INNER JOIN sys.objects o ON m.object_id=o.object_id
INNER JOIN sys.schemas s ON o.schema_id=s.schema_id
WHERE m.definition Like '%'+@SearchValue+'%'
--AND o.Type='P' --<uncomment if you only want to search procedures
ORDER BY 1
GO