compat: add some initial RHEL support

compat: add some initial RHEL support

This adds a series of CONFIG_COMPAT_${RHEL_MAJOR}_${i} tags
for each known RHEL version that we supercede. I cannot
verify if this is correct but this is my translation of
this to script:

RHEL_MAJOR := $(shell grep ^RHEL_MAJOR $(KLIB_BUILD)/Makefile | sed -n 's/.*= *\(.*\)/\1/p')
ifneq ($(RHEL_MAJOR),)
RHEL_MINOR := $(shell grep ^RHEL_MINOR $(KLIB_BUILD)/Makefile | sed -n 's/.*= *\(.*\)/\1/p')
COMPAT_RHEL_VERSIONS := $(shell I=$(RHEL_MINOR); while [ "$$I" -ge 0 ]; do echo $$I; I=$$(($$I - 1)); done)
$(foreach ver,$(COMPAT_RHEL_VERSIONS),$(eval CONFIG_COMPAT_RHEL_$(RHEL_MAJOR)_$(ver)=y))

Cc: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@frijolero.org>