firmware: xilinx: Fix dereferencing freed memory

Fix smatch warning:
drivers/firmware/xilinx/zynqmp.c:1288 zynqmp_firmware_remove()
error: dereferencing freed memory 'feature_data'

Use hash_for_each_safe for safe removal of hash entry.

Fixes: acfdd185 ("firmware: xilinx: Use hash-table for api feature check")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tejas Patel <tejas.patel@xilinx.com>
Signed-off-by: Rajan Vaja <rajan.vaja@xilinx.com>
Link: https://lore.kernel.org/r/1612765883-22018-1-git-send-email-rajan.vaja@xilinx.com


Signed-off-by: Michal Simek <michal.simek@xilinx.com>