sandbox: use correct type reading /proc/self/maps

Compiling arch/sandbox/cpu/os.c results in an error

../arch/sandbox/cpu/os.c: In function ‘os_find_text_base’:
../arch/sandbox/cpu/os.c:823:12: error: cast to pointer from
integer of different size [-Werror=int-to-pointer-cast]
  823 |     base = (void *)addr;
      |            ^
cc1: all warnings being treated as errors

The size of void* differs from that of unsigned long long on 32bit
systems.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/cpu/os.c b/arch/sandbox/cpu/os.c
index 47dfb47..79094fb 100644
--- a/arch/sandbox/cpu/os.c
+++ b/arch/sandbox/cpu/os.c
@@ -816,10 +816,10 @@
 		char *end = memchr(line, '-', len);
 
 		if (end) {
-			unsigned long long addr;
+			uintptr_t addr;
 
 			*end = '\0';
-			if (sscanf(line, "%llx", &addr) == 1)
+			if (sscanf(line, "%zx", &addr) == 1)
 				base = (void *)addr;
 		}
 	}