all archs: consolidate init and exit sections in vmlinux.lds.h

This patch consolidate all definitions of .init.text, .init.data
and .exit.text, .exit.data section definitions in
the generic vmlinux.lds.h.

This is a preparational patch - alone it does not buy
us much good.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

arch/um/kernel/dyn.lds.S

@@ -17,7 +17,7 @@ SECTIONS
   __init_begin = .;
   .init.text : {
 	_sinittext = .;
-	*(.init.text)
+	INIT_TEXT
 	_einittext = .;
   }
 
@@ -84,7 +84,7 @@ SECTIONS
 
   #include "asm/common.lds.S"
 
-  init.data : { *(.init.data) }
+  init.data : { INIT_DATA }
 
   /* Ensure the __preinit_array_start label is properly aligned.  We
      could instead move the label definition inside the section, but