grep -2 fclock arch/arm/mach-omap2/board-rx51-video.c

static struct sgx_platform_data rx51_sgx_data = {
.fclock_max = 110666666,
};

I don't know if it is capped on chip or not. Without fclock_max it defaults to 87MHz if memory serves. How it affects battery life I can't say, there is power management though.