kernel: syscalls: Change handlers namespace

According C99 the first 31 characters of an identifier must be unique.
Shortening the namespace of the generated objects to achieve it.

C99 - 5.2.4.1
MISRA-C rule 5.1

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
diff --git a/scripts/gen_syscalls.py b/scripts/gen_syscalls.py
index c919802..957bf14 100755
--- a/scripts/gen_syscalls.py
+++ b/scripts/gen_syscalls.py
@@ -149,7 +149,7 @@
 
     invocation = "%s(%s)" % (macro, argslist)
 
-    handler = "_handler_" + func_name
+    handler = "hdlr_" + func_name
 
     # Entry in _k_syscall_table
     table_entry = "[%s] = %s" % (sys_id, handler)