MDEV-21225: Fix warnings

Datafile::find_space_id(): Remove an unused variable

buf_chunk_init(): warning C4319:  '~': zero extending 'ulong' to 'ulint'
of greater size

storage/innobase/buf/buf0buf.cc

@@ -1605,7 +1605,7 @@ buf_chunk_init(
 
 	frame = reinterpret_cast<byte*>((reinterpret_cast<ulint>(chunk->mem)
 					 + srv_page_size - 1)
-					& ~(srv_page_size - 1));
+					& ~ulint{srv_page_size - 1});
 	chunk->size = (chunk->mem_pfx.m_size >> srv_page_size_shift)
 		- (frame != chunk->mem);
 

storage/innobase/fsp/fsp0file.cc

@@ -673,8 +673,7 @@ Datafile::find_space_id()
 		}
 
 		for (ulint j = 0; j < page_count; ++j) {
-			if (dberr_t err = os_file_read(
-				    IORequestRead, m_handle, page,
+			if (os_file_read(IORequestRead, m_handle, page,
 					 j * page_size, page_size)) {
 				ib::info()
 					<< "READ FAIL: page_no:" << j;