rng: msm: don't enable PRNG if it's already enabled

rng: msm: don't enable PRNG if it's already enabled

msm_rng_enable is supposed to skip writing to LFSR_CFG + CONFIG
registers in the PRNG_ block if PRNG_CONFIG_HW_ENABLE is already set.
The logic to test for this was inverted.

Without this fix, the driver was causing SError aborts on my MSM8916
device. Stephan Gerhold suggested this was probably because TZ has
marked this as a protected register, since it would also be using it for
RNG.

Fixes: 033ec636fcb ("rng: Add Qualcomm MSM PRNG driver")
Suggested-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Sam Day <me@samcday.com>
Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>
Link: https://lore.kernel.org/r/20250212-msm-rng-fixes-v2-3-645cf8d3fd3c@samcday.com
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>