ext4: fix data offset overflow on 32-bit archs in ext4_inline_data_fiemap()

On 32-bit archs when sector_t is defined as 32-bit the logic computing
data offset in ext4_inline_data_fiemap(). Fix that by properly typing
the shifted value.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>