Amend memory layout to match tock 1.5 release

boards/layout_nrf52.ld

diff --git a/boards/layout_nrf52.ld b/boards/layout_nrf52.ld
index 419a0bc..40cdb10 100644
--- a/boards/layout_nrf52.ld
+++ b/boards/layout_nrf52.ld
@@ -3,7 +3,7 @@
 MEMORY {
   /* The application region is 64 bytes (0x40) */
   FLASH (rx) : ORIGIN = 0x00030040, LENGTH = 0x0005FFC0
-  SRAM (rwx) : ORIGIN = 0x20002000, LENGTH = 62K
+  SRAM (rwx) : ORIGIN = 0x20004000, LENGTH = 62K
 }
 
 /*