Documentation: embargoed-hardware-issues.rst: Add myself for Power

Unfortunately Anton has left IBM. Add myself as the contact for Power,
until someone else volunteers.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20240322103840.668746-1-mpe@ellerman.id.auSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/process/embargoed-hardware-issues.rst

@@ -252,7 +252,7 @@ an involved disclosed party. The current ambassadors list:
   AMD		Tom Lendacky <thomas.lendacky@amd.com>
   Ampere	Darren Hart <darren@os.amperecomputing.com>
   ARM		Catalin Marinas <catalin.marinas@arm.com>
-  IBM Power	Anton Blanchard <anton@linux.ibm.com>
+  IBM Power	Michael Ellerman <ellerman@au.ibm.com>
   IBM Z		Christian Borntraeger <borntraeger@de.ibm.com>
   Intel		Tony Luck <tony.luck@intel.com>
   Qualcomm	Trilok Soni <quic_tsoni@quicinc.com>