clk: mediatek: Remove ifr{0,1}_cfg_regs structures

These aren't used and the macros that reference them aren't used either.
Remove the dead code to avoid compile warnings.

Cc: Owen Chen <owen.chen@mediatek.com>
Cc: Mars Cheng <mars.cheng@mediatek.com>
Cc: Macpaul Lin <macpaul.lin@mediatek.com>
Fixes: 1aca9939 ("clk: mediatek: Add MT6765 clock support")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20200609211847.27366-1-sboyd@kernel.org