sandbox: Make map_to_sysmem() use a constant pointer

Very often a constant pointer is passed to this function, so we should
declare this, since map_to_sysmem() does not change the pointer.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/include/asm/io.h

diff --git a/arch/sandbox/include/asm/io.h b/arch/sandbox/include/asm/io.h
index 9ac6a5f..7956041 100644
--- a/arch/sandbox/include/asm/io.h
+++ b/arch/sandbox/include/asm/io.h
@@ -38,6 +38,6 @@
 }
 
 /* Map from a pointer to our RAM buffer */
-phys_addr_t map_to_sysmem(void *ptr);
+phys_addr_t map_to_sysmem(const void *ptr);
 
 #endif

include/common.h

diff --git a/include/common.h b/include/common.h
index 409515f..8ca67f6 100644
--- a/include/common.h
+++ b/include/common.h
@@ -923,7 +923,7 @@
 {
 }
 
-static inline phys_addr_t map_to_sysmem(void *ptr)
+static inline phys_addr_t map_to_sysmem(const void *ptr)
 {
 	return (phys_addr_t)(uintptr_t)ptr;
 }