picolib/arm: Clean up read_tp function

Use built-in assembler symbol reference mechanism

Signed-off-by: Keith Packard <[email protected]>
diff --git a/newlib/libc/picolib/machine/arm/read_tp.S b/newlib/libc/picolib/machine/arm/read_tp.S
index 78258db..a20e920 100644
--- a/newlib/libc/picolib/machine/arm/read_tp.S
+++ b/newlib/libc/picolib/machine/arm/read_tp.S
@@ -54,16 +54,10 @@
 	mrc 15, 0, r0, c13, c0, 3
 #else
 	/* Load the address of __tls */
-	ldr r0,1f
+	ldr r0,=__tls
 	/* Dereference to get the value of __tls */
 	ldr r0,[r0]
 #endif
 	/* All done, return to caller */
 	bx lr
 	.cfi_endproc
-	
-	/* Holds the address of __tls */
-	.align 2
-#ifndef ARM_TLS_CP15
-1: .word __tls
-#endif