Solution:
No, you cannot program SRAM in SLAVE SPI(SSPI) mode. SSPI can only be utilized to program and verify an encrypted or standard JEDEC file into embedded configuration Flash in background mode. It can be used to read the SRAM fuse cells in background mode only.
SRAM programming is available using either the master SPI(MSPI) sysConfig port or JTAG 1149 TAP port.
For more information please reference the following documents.
LatticeXP2 Family Datasheet http://www.latticesemi.com/documents/DS1009.pdff
LatticeXP2 sysCONFIG Usage Guide http://www.latticesemi.com/documents/TN1141.pdf
LatticeXP2 Slave SPI Port User's Guide http://www.latticesemi.com/documents/TN1213.pdf