tegra124: Reserve secure RAM using MC_SECURITY_CFG{0, 1}_0

These registers can be used to prevent non-secure world from accessing a
megabyte aligned region of RAM, use them to protect the u-boot secure monitor
code.

At first I tried to do this from s_init(), however this inexplicably causes
u-boot's networking (e.g. DHCP) to fail, while networking under Linux was fine.

So instead I have added a new weak arch function protect_secure_section()
called from relocate_secure_section() and reserved the region there. This is
better overall since it defers the reservation until after the sec vs. non-sec
decision (which can be influenced by an envvar) has been made when booting the
os.

Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
[Jan: tiny style adjustment]
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Tested-by: Ian Campbell <ijc@hellion.org.uk>
Signed-off-by: Tom Warren <twarren@nvidia.com>

arch/arm/cpu/armv7/virt-v7.c

@@ -46,6 +46,10 @@ static unsigned long get_gicd_base_address(void)
 #endif
 }
 
+/* Define a specific version of this function to enable any available
+ * hardware protections for the reserved region */
+void __weak protect_secure_section(void) {}
+
 static void relocate_secure_section(void)
 {
 #ifdef CONFIG_ARMV7_SECURE_BASE
@@ -54,6 +58,7 @@ static void relocate_secure_section(void)
 	memcpy((void *)CONFIG_ARMV7_SECURE_BASE, __secure_start, sz);
 	flush_dcache_range(CONFIG_ARMV7_SECURE_BASE,
 			   CONFIG_ARMV7_SECURE_BASE + sz + 1);
+	protect_secure_section();
 	invalidate_icache_all();
 #endif
 }