MAINTAINERS: add "hw/registerfields.h" in Register API entry

Orphan since afb3141cSigned-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NDarren Kenny <darren.kenny@oracle.com>
Reviewed-by: NAlistair Francis <alistair.francis@xilinx.com>
Reviewed-by: NEdgar E. Iglesias <edgar.iglesias@xilinx.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

MAINTAINERS

@@ -1538,6 +1538,7 @@ M: Alistair Francis <alistair.francis@xilinx.com>
 S: Maintained
 F: hw/core/register.c
 F: include/hw/register.h
+F: include/hw/registerfields.h
 
 SLIRP
 M: Samuel Thibault <samuel.thibault@ens-lyon.org>