rename files acc_ramp.* -> acc.c*

With upcoming next commit, the file will contain far more code that
simply ramping, so rename it to be more generic.

Change-Id: I8c368ab87e264439dea4ccf556821a44664cdbb0
diff --git a/include/osmocom/bsc/Makefile.am b/include/osmocom/bsc/Makefile.am
index c2a82ce..1ee96ed 100644
--- a/include/osmocom/bsc/Makefile.am
+++ b/include/osmocom/bsc/Makefile.am
@@ -3,7 +3,7 @@
 	abis_nm.h \
 	abis_om2000.h \
 	abis_rsl.h \
-	acc_ramp.h \
+	acc.h \
 	arfcn_range_encode.h \
 	assignment_fsm.h \
 	bsc_rll.h \