env: Use static_assert() to check if default_environment is too large

Check sizeof(default_environment) against ENV_SIZE in a static_assert()
instead of runtime.
Only check if !USE_HOSTCC (for in fw_env tool ENV_SIZE expands to a
variable, and cannot be checked statically) nad
!DEFAULT_ENV_INSTANCE_EMBEDDED, for in that case the default_environment
variable is not set.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Simon Glass <sjg@chromium.org>

env/common.c

@@ -247,11 +247,6 @@ char *env_get_default(const char *name)
 
 void env_set_default(const char *s, int flags)
 {
-	if (sizeof(default_environment) > ENV_SIZE) {
-		puts("*** Error - default environment is too large\n\n");
-		return;
-	}
-
 	if (s) {
 		if ((flags & H_INTERACTIVE) == 0) {
 			printf("*** Warning - %s, "