clk: imx: rename imx_obtain_fixed_clk_hw() to imx_get_clk_hw_by_name()

The imx_obtain_fixed_clk_hw name was wrong and misleading. Renaming it
to imx_get_clk_hw_by_name clarifies the purpose of the function, and
will allow it to be used not only for fixed rate clocks but also in
wider contexts.

No functional changes intended.

The replacements were made with the following command:

grep -rl 'imx_obtain_fixed_clk_hw' ./ | \
     xargs sed -i 's/imx_obtain_fixed_clk_hw/imx_get_clk_hw_by_name/g'

Tested on a BSH SystemMaster (SMM) S2 board.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20221113180839.1625832-1-dario.binacchi@amarulasolutions.com