MAINTAINERS: Fix label for 'Nuvoton_NPCX Platforms'

This commit updates the label name in the 'Nuvoton_NPCX Platforms'
entry to match the actual GitHub label name, which is 'platform:
Nuvoton NPCX Platforms'.

In addition, the entry name is also updated to match the label styling
(underscore is removed).

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

MAINTAINERS.yml

@@ -1527,7 +1527,7 @@ Synopsys Platforms:
     labels:
         - "platform: Synopsys"
 
-Nuvoton_NPCX Platforms:
+Nuvoton NPCX Platforms:
     status: maintained
     maintainers:
         - MulinChao
@@ -1549,7 +1549,7 @@ Nuvoton_NPCX Platforms:
         - dts/bindings/*/*npcx*
         - drivers/*/*_npcx*.c
     labels:
-        - "platform: Nuvoton_NPCX"
+        - "platform: Nuvoton NPCX"
 
 Nuvoton_Numicro Platforms:
     status: odd fixes