mailbox: zynqmp-ipi: Fix out-of-bounds access in mailbox cleanup loop

In the Linux kernel, the following vulnerability has been resolved: mailbox: zynqmp-ipi: Fix out-of-bounds access in mailbox cleanup loop The cleanup loop was starting at the wrong array index, causing out-of-bounds access. Start the loop at the correct index for zero-indexed arrays to prevent accessing memory beyond the allocated array bounds.