firmware/layer1: avoid 'for' loop initial declarations
As was reported by roox, osmocom-bb currently fails to build on OBS:
https://build.opensuse.org/build/home:mnhauke:osmocom:nightly/openSUSE_Tumbleweed/x86_64/osmocom-bb/_log
[ 24s] layer1/prim_tch.c: In function 'l1s_tch_meas_avg':
[ 24s] layer1/prim_tch.c:183:2: error: 'for' loop initial declarations are only allowed in C99 mode
[ 24s] layer1/prim_tch.c:183:2: note: use option -std=c99 or -std=gnu99 to compile your code
We don't specify the C standard explicitly, so let's move the variable
declaration out of the for-loop in l1s_tch_meas_avg().
Change-Id: I6c65fbead4e612c81728e9c6601d5f2107616ee6
Fixes:
7286560a3 "firmware/layer1: fill-in DL info for L1CTL TRAFFIC.ind"