Revert "serial: sirf: add a new uart type support"

This reverts commit 52bec4ed4e("serial: sirf: add a new uart type
support").
we misunderstood the clock dependency in atlas7. Actually involved
several clocks are in a tree structure. we still only need to take
the leaf clock node for BT uarts.

Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Barry.Song@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>