firmware: arm_sdei: remove unused interfaces

The export symbols to register/unregister and enable/disable events
aren't used upstream, remove them.

[ dropped the parts of Christoph's patch that made the API static too ]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Morse <james.morse@arm.com>
Link: https://lore.kernel.org/linux-arm-kernel/20200504164224.2842960-1-hch@lst.de/
Link: https://lore.kernel.org/r/20200519182108.13693-3-james.morse@arm.comSigned-off-by: Will Deacon <will@kernel.org>

drivers/firmware/arm_sdei.c

@@ -429,7 +429,6 @@ int sdei_event_enable(u32 event_num)
 
 	return err;
 }
-EXPORT_SYMBOL(sdei_event_enable);
 
 static int sdei_api_event_disable(u32 event_num)
 {
@@ -471,7 +470,6 @@ int sdei_event_disable(u32 event_num)
 
 	return err;
 }
-EXPORT_SYMBOL(sdei_event_disable);
 
 static int sdei_api_event_unregister(u32 event_num)
 {
@@ -533,7 +531,6 @@ int sdei_event_unregister(u32 event_num)
 
 	return err;
 }
-EXPORT_SYMBOL(sdei_event_unregister);
 
 /*
  * unregister events, but don't destroy them as they are re-registered by
@@ -643,7 +640,6 @@ int sdei_event_register(u32 event_num, sdei_event_callback *cb, void *arg)
 
 	return err;
 }
-EXPORT_SYMBOL(sdei_event_register);
 
 static int sdei_reregister_event_llocked(struct sdei_event *event)
 {