imx233: generate register headers using headergen_v2 and update code for it

NOTE: this commit does not introduce any change, ideally even the binary should
be almost the same. I checked the disassembly by hand and there are only a few
differences here and there, mostly the compiler decides to compile very close
expressions slightly differently. I tried to run the new code on several targets
to make sure and saw no difference.

The major syntax changes of the new headers are as follows:
- BF_{WR,SET,CLR} are now superpowerful and allows to set several fileds at once:
  BF_WR(reg, field1(value1), field2(value2), ...)
- BF_CS (use like BF_WR) does a write to reg_CLR and then reg_SET instead of RMW
- there is no more need for macros like BF_{WR_,SET,CLR}_V, since one can simply
  BF_WR with field_V(name)
- the old BF_SETV macro has no trivial equivalent and is replaced with its
  its equivalent for BF_WR(reg_SET, ...)

I also rename the register headers: "regs/regs-x.h" -> "regs/x.h" to avoid the
redundant "regs".

Final note: the registers were generated using the following command:
./headergen_v2 -g imx -o ../../firmware/target/arm/imx233/regs/ desc/regs-stmp3{600,700,780}.xml

Change-Id: I7485e8b4315a0929a8edb63e7fa1edcaa54b1edc

firmware/target/arm/imx233/button-imx233.h

@@ -101,11 +101,11 @@ struct imx233_button_map_t
 #define IMX233_BUTTON_NAMEFLAGS3(_,name_,f1,f2)   .name = name_, \
     .flags = IMX233_BUTTON_##f1 | IMX233_BUTTON_##f2
 #define IMX233_BUTTON_NAMEFLAGS4(_,name_,f1,f2,f3)    .name = name_, \
-    .flags =IMX233_BUTTON_##f1 | IMX233_BUTTON_##f2 | IMX233_BUTTON_##f3
+    .flags = IMX233_BUTTON_##f1 | IMX233_BUTTON_##f2 | IMX233_BUTTON_##f3
 
 #define IMX233_BUTTON__(btn_, path_, ...) \
     {.btn = btn_, IMX233_BUTTON_PATH_##path_, \
-     REG_VARIADIC(IMX233_BUTTON_NAMEFLAGS, dummy, __VA_ARGS__)}
+     __VAR_EXPAND(IMX233_BUTTON_NAMEFLAGS, dummy, __VA_ARGS__)}
 #define IMX233_BUTTON_(btn_, path_, ...) \
     IMX233_BUTTON__(IMX233_BUTTON_##btn_, path_, __VA_ARGS__)
 #define IMX233_BUTTON(btn_, path_, ...) \