misc: Fix coding style for enum's opening braces

The systemc dir was not included in this fix.

First it was identified that there were only occurrences
at 0, 1, and 2 levels of indentation (and 2 of 2 spaces,
1 of 3 spaces and 2 of 12 spaces), using:

    grep -nrE --exclude-dir=systemc \
        "^ *enum [A-Za-z].* {$" src/

Then the following commands were run to replace:

    <indent level>enum X ... {

by:

    <indent level>enum X ...
    <indent level>{

Level 0:
    grep -nrl --exclude-dir=systemc \
        "^enum [A-Za-z].* {$" src/ | \
        xargs sed -Ei \
        's/^enum ([A-Za-z].*) \{$/enum \1\n\{/g'

Level 1:
    grep -nrl --exclude-dir=systemc \
        "^    enum [A-Za-z].* {$" src/ | \
        xargs sed -Ei \
        's/^    enum ([A-Za-z].*) \{$/    enum \1\n    \{/g'

and so on.

Change-Id: Ib186cf379049098ceaec20dfe4d1edcedd5f940d
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/43326
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/python/m5/params.py

@@ -1328,7 +1328,8 @@ class MetaEnum(MetaParamValue):
 ''')
         if cls.is_class:
             code('''\
-enum class $name {
+enum class $name
+{
 ''')
         else:
             code('''\