i2c: mpc: Remove redundant NULL check

In mpc_i2c_get_fdr_8xxx div is assigned as we iterate through the
mpc_i2c_dividers_8xxx array. By the time we exit the loop div will
either have the value that matches the requested speed or be pointing at
the last entry in mpc_i2c_dividers_8xxx. Checking for div being NULL
after the loop is redundant so remove the check.

Reported-by: Wolfram Sang <wsa@kernel.org>
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Wolfram Sang <wsa@kernel.org>