Revert "blk: Invalidate block cache when switching hwpart"

Revert "blk: Invalidate block cache when switching hwpart"

This reverts commit 49efe4994db6b69a9cf8cb93a78db848a42c9174.

Most block devices have only one hwpart. Multiple hwparts only found used
by eMMC devices in u-boot. The mmc driver do blk_dselect_hwpart() at the
beginning of mmc_bread() which causes block cache being invalidated too
frequently and makes block cache useless.

So it's not a good idea to put blkcache_invalidate() in the common
functions. It should be called inside mmc_select_hwpart().

Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
Tested-by: Felix Brack <fb@ltec.ch>