s390/ipl: cleanup macro usage
s390/ipl: cleanup macro usage

ipl.c uses 3 different macros to create a sysfs show function for ipl
attributes. Define IPL_ATTR_SHOW_FN which is used by all macros.

Reviewed-by: Michael Holzheu <db4757c56f54651f568cc7cda79cd93c781b1605@linux.vnet.ibm.com>
Signed-off-by: Sebastian Ott <34be3ca399e9e73d80098c083a5b58614c3ca6da@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <52616596d8f5df0d597e85ab515377f92f939c68@de.ibm.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs