clk: h8300: Remove impossible check for of_clk_get_parent_count()

The checks for < 1 can be simplified now that
of_clk_get_parent_count() returns an unsigned int. Update the
code to reflect the int to unsigned int change.

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: <uclinux-h8-devel@lists.sourceforge.jp>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>