can: m_can: m_can_class_allocate_dev(): initialize spin lock on device probe

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

can: m_can: m_can_class_allocate_dev(): initialize spin lock on device probe

The spin lock tx_handling_spinlock in struct m_can_classdev is not

being initialized. This leads the following spinlock bad magic

complaint from the kernel, eg. when trying to send CAN frames with

cansend from can-utils:

| BUG: spinlock bad magic on CPU#0, cansend/95

| lock: 0xff60000002ec1010, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0

| CPU: 0 UID: 0 PID: 95 Comm: cansend Not tainted 6.15.0-rc3-00032-ga79be02bba5c #5 NONE

| Hardware name: MachineWare SIM-V (DT)

| Call Trace:

| [<ffffffff800133e0>] dump_backtrace+0x1c/0x24

| [<ffffffff800022f2>] show_stack+0x28/0x34

| [<ffffffff8000de3e>] dump_stack_lvl+0x4a/0x68

| [<ffffffff8000de70>] dump_stack+0x14/0x1c

| [<ffffffff80003134>] spin_dump+0x62/0x6e

| [<ffffffff800883ba>] do_raw_spin_lock+0xd0/0x142

| [<ffffffff807a6fcc>] _raw_spin_lock_irqsave+0x20/0x2c

| [<ffffffff80536dba>] m_can_start_xmit+0x90/0x34a

| [<ffffffff806148b0>] dev_hard_start_xmit+0xa6/0xee

| [<ffffffff8065b730>] sch_direct_xmit+0x114/0x292

| [<ffffffff80614e2a>] __dev_queue_xmit+0x3b0/0xaa8

| [<ffffffff8073b8fa>] can_send+0xc6/0x242

| [<ffffffff8073d1c0>] raw_sendmsg+0x1a8/0x36c

| [<ffffffff805ebf06>] sock_write_iter+0x9a/0xee

| [<ffffffff801d06ea>] vfs_write+0x184/0x3a6

| [<ffffffff801d0a88>] ksys_write+0xa0/0xc0

| [<ffffffff801d0abc>] __riscv_sys_write+0x14/0x1c

| [<ffffffff8079ebf8>] do_trap_ecall_u+0x168/0x212

| [<ffffffff807a830a>] handle_exception+0x146/0x152

Initializing the spin lock in m_can_class_allocate_dev solves that

problem.