MAINTAINERS: exclude char maintainers from things they do not maintain

There are a number of subdirectories and files in drivers/char/ that
have their own maintainers and developers and ways of getting patches to
Linus. This includes random.c, IPMI, hardware random drivers, TPM
drivers, and agp drivers. Instead of sending those patches to Arnd and
myself, who can't do anything with them, send them to the proper
developers instead.

Acked-by: Arnd Bergmann <[e-mail]>
Acked-by: Corey Minyard <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

MAINTAINERS

···
 F:	drivers/char/
 F:	drivers/misc/
 F:	include/linux/miscdevice.h
+X:	drivers/char/agp/
+X:	drivers/char/hw_random/
+X:	drivers/char/ipmi/
+X:	drivers/char/random.c
+X:	drivers/char/tpm/
 
 CHECKPATCH
 M:	Andy Whitcroft <[e-mail]>