sample: driver: spi_flash: Add emsdp support

Add emsdp support in spi_flash driver sample
output log:
JEDEC QSPI-NOR SPI flash testing
==========================

Test 1: Flash erase
Flash erase succeeded!

Test 2: Flash write
Attempting to write 4 bytes
Data read matches data written. Good!

Signed-off-by: Siyuan Cheng <siyuanc@synopsys.com>