MAINTAINERS: generify the Microchip RISC-V entry name

These drivers work on our other FPGAs, for example the non-SoC PolarFire
connected to an FU-540 via chiplink. Make the entry a wee bit more
generic to match. While at it, remove the / from the heading so that it
matches other, neighbouring RISC-V entries.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20221109212219.1598355-3-conor@kernel.orgSigned-off-by: Arnd Bergmann <arnd@arndb.de>

MAINTAINERS

@@ -17725,7 +17725,7 @@ F:	arch/riscv/
 N:	riscv
 K:	riscv
 
-RISC-V/MICROCHIP POLARFIRE SOC SUPPORT
+RISC-V MICROCHIP FPGA SUPPORT
 M:	Conor Dooley <conor.dooley@microchip.com>
 M:	Daire McNamara <daire.mcnamara@microchip.com>
 L:	linux-riscv@lists.infradead.org