[Pal/Linux-SGX] Remove loader.nonpie_binary manifest option

Non-PIE binaries support requires ELRANGE to start at low addresses,
which on older SGX drivers required root permissions or reconfiguring
the host, so this mapping strategy was made optional by us. This issue
was fixed long time ago, so we can drop this option and always start
enclaves at 0.

python/graphenelibos/sgx_sign.py

@@ -781,12 +781,8 @@ def main_sign(args):
     # Try populate memory areas
     memory_areas = get_memory_areas(attr, args)
 
-    if manifest.get('sgx.nonpie_binary', None) == '1':
-        enclave_base = offs.DEFAULT_ENCLAVE_BASE
-        enclave_heap_min = offs.MMAP_MIN_ADDR
-    else:
-        enclave_base = attr['enclave_size']
-        enclave_heap_min = enclave_base
+    enclave_base = offs.DEFAULT_ENCLAVE_BASE
+    enclave_heap_min = offs.MMAP_MIN_ADDR
 
     if manifest.get('sgx.enable_stats', None) is None:
         manifest['sgx.enable_stats'] = '0'