osv: properly assign gsi number inside handler

Initialize the gsi number inside handler to an unreachable number. The
gsi number was not properly initialized and default to 0 previously, and
caused interrupt misfiring for level triggered interrupts on pin 0 when
it checks for the gsi number for interrupt sharing. This commit fixed
the misfiring on pin 0.

Fixes: 5fc9daf ("interrupt: Support interrupt sharing")
Signed-off-by: YuChen Qian <yuchenq@amazon.de>
Reviewed-by: Amadeusz Juskowiak <ajusk@amazon.de>
Reviewed-by: Marius Hillenbrand <mhillenb@amazon.de>
Cc-Team: kaos-brimstone <kaos-brimstone@amazon.com>

CR: https://code.amazon.com/reviews/CR-14472907
Message-Id: <20191204084413.5400-1-yuchenq@amazon.de>

Author: yuchen-96

arch/x64/exceptions.hh

@@ -117,6 +117,7 @@ private:
                     break;
                 }
             }
+            gsi = -1u;
         }
 
         handler(handler *h,
@@ -131,6 +132,7 @@ private:
             ids.push_back(id++);
             pre_eois.push_back(_pre_eoi);
             post_eois.push_back(_post_eoi);
+            gsi = -1u;
         }
 
         unsigned size()