clk: qcom: clk-rpmh: prevent integer overflow in recalc_rate

clk: qcom: clk-rpmh: prevent integer overflow in recalc_rate

aggr_state and unit fields are u32. The result of their
multiplication may not fit in this type.

Add explicit casting to prevent overflow.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 04053f4d23a4 ("clk: qcom: clk-rpmh: Add IPA clock support")
Cc: stable@vger.kernel.org # 5.4+
Signed-off-by: Anastasia Belova <abelova@astralinux.ru>
Link: https://lore.kernel.org/r/20241203084231.6001-1-abelova@astralinux.ru
Signed-off-by: Bjorn Andersson <andersson@kernel.org>