hwmon: msm_adc: Fix section mismatches

WARNING: drivers/hwmon/built-in.o(.text+0x1204): Section mismatch
in reference from the function msm_adc_probe() to the function
.devinit.text:msm_rpc_adc_init()
The function msm_adc_probe() references
the function __devinit msm_rpc_adc_init().
This is often because msm_adc_probe lacks a __devinit
annotation or the annotation of msm_rpc_adc_init is wrong.

Change-Id: I277124f27f732bdf411533225459cd26c39572eb
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>