clk: ti: dflt: remove redundant unlikely

Commit 7aba4f52 ("clk: ti: dflt: fix enable_reg validity check")
fixed a validation check by using an IS_ERR() macro within the
existing unlikely expression, but IS_ERR() macro already has an
unlikely inside it, so get rid of the redundant unlikely macro
from the validation check.

Reported-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>