isdn/hisax: amd7930_fn: Remove unnecessary parentheses

Clang warns when multiple sets of parentheses are used for a single
conditional statement.

drivers/isdn/hisax/amd7930_fn.c:628:32: warning: equality comparison
with extraneous parentheses [-Wparentheses-equality]
                if ((cs->dc.amd7930.ph_state == 8)) {
                     ~~~~~~~~~~~~~~~~~~~~~~~~^~~~
drivers/isdn/hisax/amd7930_fn.c:628:32: note: remove extraneous
parentheses around the comparison to silence this warning
                if ((cs->dc.amd7930.ph_state == 8)) {
                    ~                        ^   ~
drivers/isdn/hisax/amd7930_fn.c:628:32: note: use '=' to turn this
equality comparison into an assignment
                if ((cs->dc.amd7930.ph_state == 8)) {
                                             ^~
                                             =
1 warning generated.

Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>