target: Remove WEAK definition of target_read_panel_signature

Function target_read_panel_signature to be moved to msm shared.
Hence remove WEAK definition from target init.

Change-Id: I37d9268971d6050913c995ef5cec1b1111a5ae5b
diff --git a/target/init.c b/target/init.c
index 92bcf04..7875a4f 100644
--- a/target/init.c
+++ b/target/init.c
@@ -120,11 +120,6 @@
 {
 }
 
-__WEAK uint32_t target_read_panel_signature(uint32_t panel_signature)
-{
-	return 0;
-}
-
 /* Default target does not support continuous splash screen feature. */
 __WEAK int target_cont_splash_screen()
 {