UM: cpuinfo: Fix a warning for CONFIG_CPUMASK_OFFSTACK

In the Linux kernel, the following vulnerability has been resolved:

UM: cpuinfo: Fix a warning for CONFIG_CPUMASK_OFFSTACK

When CONFIG_CPUMASK_OFFSTACK and CONFIG_DEBUG_PER_CPU_MAPS is selected,

cpu_max_bits_warn() generates a runtime warning similar as below while

we show /proc/cpuinfo. Fix this by using nr_cpu_ids (the runtime limit)

instead of NR_CPUS to iterate CPUs.

[ 3.052463] ------------[ cut here ]------------

[ 3.059679] WARNING: CPU: 3 PID: 1 at include/linux/cpumask.h:108 show_cpuinfo+0x5e8/0x5f0

[ 3.070072] Modules linked in: efivarfs autofs4

[ 3.076257] CPU: 0 PID: 1 Comm: systemd Not tainted 5.19-rc5+ #1052

[ 3.099465] Stack : 9000000100157b08 9000000000f18530 9000000000cf846c 9000000100154000

[ 3.109127] 9000000100157a50 0000000000000000 9000000100157a58 9000000000ef7430

[ 3.118774] 90000001001578e8 0000000000000040 0000000000000020 ffffffffffffffff

[ 3.128412] 0000000000aaaaaa 1ab25f00eec96a37 900000010021de80 900000000101c890

[ 3.138056] 0000000000000000 0000000000000000 0000000000000000 0000000000aaaaaa

[ 3.147711] ffff8000339dc220 0000000000000001 0000000006ab4000 0000000000000000

[ 3.157364] 900000000101c998 0000000000000004 9000000000ef7430 0000000000000000

[ 3.167012] 0000000000000009 000000000000006c 0000000000000000 0000000000000000

[ 3.176641] 9000000000d3de08 9000000001639390 90000000002086d8 00007ffff0080286

[ 3.186260] 00000000000000b0 0000000000000004 0000000000000000 0000000000071c1c

[ 3.195868] ...

[ 3.199917] Call Trace:

[ 3.203941] [<90000000002086d8>] show_stack+0x38/0x14c

[ 3.210666] [<9000000000cf846c>] dump_stack_lvl+0x60/0x88

[ 3.217625] [<900000000023d268>] __warn+0xd0/0x100

[ 3.223958] [<9000000000cf3c90>] warn_slowpath_fmt+0x7c/0xcc

[ 3.231150] [<9000000000210220>] show_cpuinfo+0x5e8/0x5f0

[ 3.238080] [<90000000004f578c>] seq_read_iter+0x354/0x4b4

[ 3.245098] [<90000000004c2e90>] new_sync_read+0x17c/0x1c4

[ 3.252114] [<90000000004c5174>] vfs_read+0x138/0x1d0

[ 3.258694] [<90000000004c55f8>] ksys_read+0x70/0x100

[ 3.265265] [<9000000000cfde9c>] do_syscall+0x7c/0x94

[ 3.271820] [<9000000000202fe4>] handle_syscall+0xc4/0x160

[ 3.281824] ---[ end trace 8b484262b4b8c24c ]---