ext2fs: add ext2_getpages().

Literally copy/pasted from ffs_getpages().

Tested with:	fsx
MFC after:	2 months


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271467 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Extra space from r271467.

MFC after:	2 months


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271468 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f