drc: align tcache_default to 64k on arm

Newer arm64 hw supports 64k pages, and recent Linux distros provide
kernel packages like linux-image-generic-64k (can be used on r-pi4
with Ubuntu for example). It affects 32bit mode also, so assume that
an arm32 binary compiled for vfp may be used on such kernel.

Without this mprotect() fails to set exec permission because of bad
alignment.

cpu/drc/cmn.c

@@ -10,7 +10,13 @@
 #include <pico/pico_int.h>
 #include "cmn.h"
 
-u8 ALIGNED(4096) tcache_default[DRC_TCACHE_SIZE];
+#if defined(__aarch64__) || defined(__VFP_FP__)
+// might be running on a 64k-page kernel
+#define PICO_PAGE_ALIGN 65536
+#else
+#define PICO_PAGE_ALIGN 4096
+#endif
+u8 ALIGNED(PICO_PAGE_ALIGN) tcache_default[DRC_TCACHE_SIZE];
 u8 *tcache;
 
 void drc_cmn_init(void)