drm/radeon: Clean up errors in evergreen.c

Fix the following errors reported by checkpatch:

ERROR: that open brace { should be on the previous line
ERROR: spaces required around that '&=' (ctx:WxO)
ERROR: space required before that '~' (ctx:OxV)
ERROR: space prohibited before that close parenthesis ')'
ERROR: space required after that ',' (ctx:WxO)
ERROR: space required before that '&' (ctx:OxV)
ERROR: need consistent spacing around '*' (ctx:VxW)

Signed-off-by: GuoHua Chen <chenguohua_716@163.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>