clk: mmp: pxa168: Fix memory leak in pxa168_clk_init()

clk: mmp: pxa168: Fix memory leak in pxa168_clk_init()

In cases where mapping of mpmu/apmu/apbc registers fails, the code path
does not handle the failure gracefully, potentially leading to a memory
leak. This fix ensures proper cleanup by freeing the allocated memory
for 'pxa_unit' before returning.

Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Link: https://lore.kernel.org/r/20231210175232.3414584-1-visitorckw@gmail.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>