MAINTAINERS: Remove self from powerpc EEH

I'm sorry to say I can no longer maintain this position.
Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/aec7d729c28e35c7fa9969ec50229080c771195c.1593471043.git.sbobroff@linux.ibm.com

MAINTAINERS

@@ -13187,7 +13187,6 @@ F:	tools/pci/
 
 PCI ENHANCED ERROR HANDLING (EEH) FOR POWERPC
 M:	Russell Currey <ruscur@russell.cc>
-M:	Sam Bobroff <sbobroff@linux.ibm.com>
 M:	Oliver O'Halloran <oohall@gmail.com>
 L:	linuxppc-dev@lists.ozlabs.org
 S:	Supported