adc_emul: case can not run on native_posix board
we meet hardfault when run on real board.
as the device is a virtual device
I: adc init done
*** Booting Zephyr OS build zephyr-v2.5.0-3761-g730acbd6ed85 ***
Running test suite adc_basic_test
===================================================================
START - test_adc_emul_single_value
E: ***** BUS FAULT *****
E: Precise data bus error
E: BFAR Address: 0x20002d00
E: NXP MPU error, port 3
E: Mode: User, Data Address: 0x20002d00
E: Type: Read, Master: 0, Regions: 0x8100
E: r0/a1: 0x20002cfc r1/a2: 0x00000000 r2/a3: 0x000005dc
E: r3/a4: 0x00000040 r12/ip: 0x0000c67d r14/lr: 0x00001319
E: xpsr: 0x41000000
E: Faulting instruction address (r15/pc): 0x000045c6
E: >>> ZEPHYR FATAL ERROR 0: CPU exception on CPU 0
E: Current thread: 0x200000e0 (unknown)
E: Halting system
Fixes #35027
Signed-off-by: Hake Huang <hake.huang@oss.nxp.com>