ARM: dts: qcom: Remove GCC_MSS_AXIS2 clock from modem PIL for SDM845

GCC_MSS_AXIS2 clock was used for disabling boot IMEM. Boot IMEM disable
is now under the control of TZ and the clock enabling/disabling has also
been transferred to being under the control of TZ as well.

Change-Id: I8acf98bc6e9ad555ab807639f13bc208a96cddd4
Signed-off-by: Kyle Yan <kyan@codeaurora.org>