ld: support ".ramtext" section hook to place functions in ram

We already had the hooks for ccmram and ram1 and ram2 and ram3 and xsram
for "other" ram sections, but there was no method, out of the box, for
placing a function in "normal" ram.  The "easy" method of labelling a
function as ".data.someramfunc" causes warnings because code isn't meant
to have a name like ".data*" so we must explicitly add a new code
section.

Signed-off-by: Karl Palsson <karlp@tweak.net.au>

ld/linker.ld.S

@@ -127,6 +127,7 @@ SECTIONS
 	.data : {
 		_data = .;
 		*(.data*)	/* Read-write initialized data */
+		*(.ramtext*)	/* "text" functions to run in ram */
 		. = ALIGN(4);
 		_edata = .;
 	} >ram AT >rom

lib/cortex-m-generic.ld

@@ -98,6 +98,7 @@ SECTIONS
 	.data : {
 		_data = .;
 		*(.data*)	/* Read-write initialized data */
+		*(.ramtext*)    /* "text" functions to run in ram */
 		. = ALIGN(4);
 		_edata = .;
 	} >ram AT >rom