target/arm: Disable has_el2 and has_el3 for user-only

target/arm: Disable has_el2 and has_el3 for user-only

In arm_cpu_reset, we configure many system registers so that user-only
behaves as it should with a minimum of ifdefs.  However, we do not set
all of the system registers as required for a cpu with EL2 and EL3.

Disabling EL2 and EL3 mean that we will not look at those registers,
which means that we don't have to worry about configuring them.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200229012811.24129-4-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>