prima:  Switch to prima_legacy from Sony msm8x60 kernel

Based on our firmware file sizes (28456 bytes instead of 29776),
it appears we have legacy Prima firmware, and need the legacy driver.

Change-Id: I686757e5dad7e15241844eb7799f5ab24e08c090
config: Switch to legacy Prima driver

Change-Id: I812ae0c608ad37a326e095b2b1f7444a17e3f9f0