MLK-15300-1 perf: fixed crash when irq have not assigned in dts file

MLK-15300-1 perf: fixed crash when irq have not assigned in dts file

[ 28.061044] perf[2494]: PC Alignment exception: pc=0000000072656d69 sp=ffff800032f2bd30
[ 28.069061] Internal error: Oops - SP/PC alignment exception: 8a000000 1 PREEMPT SMP
[ 28.077066] Modules linked in:
[ 28.080128] CPU: 2 PID: 2494 Comm: perf Not tainted 4.9.11-02540-g3ebe22c #52
[ 28.087263] Hardware name: Freescale i.MX8QXP LPDDR4 ARM2 (DT)
[ 28.093093] task: ffff80002e097080 task.stack: ffff800032f28000
[ 28.099011] PC is at 0x72656d69
[ 28.102163] LR is at perf_try_init_event+0x98/0xb0
[ 28.106950] pc : [<0000000072656d69>] lr : [<ffff0000081594e0>] pstate: 60000145

Signed-off-by: Frank Li <Frank.Li@nxp.com>