avr32/config.mk: simplify PLATFORM_RELFLAGS

This patch removes PLATFORM_RELFLAGS from board specific config.mk files and
define them in arch specific config.mk file.
Signed-off-by: NAndreas Bießmann <biessmann@corscience.de>

arch/avr32/config.mk

@@ -26,4 +26,6 @@ CROSS_COMPILE ?= avr32-linux-
 CONFIG_STANDALONE_LOAD_ADDR ?= 0x00000000
 
 PLATFORM_RELFLAGS	+= -ffixed-r5 -fPIC -mno-init-got -mrelax
+PLATFORM_RELFLAGS	+= -ffunction-sections -fdata-sections
+
 LDFLAGS_u-boot		= --gc-sections --relax

board/atmel/atngw100/config.mk

 CONFIG_SYS_TEXT_BASE		= 0x00000000
-PLATFORM_RELFLAGS	+= -ffunction-sections -fdata-sections

board/atmel/atstk1000/config.mk

-PLATFORM_RELFLAGS	+= -ffunction-sections -fdata-sections
 CONFIG_SYS_TEXT_BASE		= 0x00000000

board/earthlcd/favr-32-ezkit/config.mk

-PLATFORM_RELFLAGS	+= -ffunction-sections -fdata-sections
 CONFIG_SYS_TEXT_BASE		= 0x00000000

board/mimc/mimc200/config.mk

 CONFIG_SYS_TEXT_BASE		= 0x00000000
-PLATFORM_RELFLAGS	+= -ffunction-sections -fdata-sections

board/miromico/hammerhead/config.mk

 CONFIG_SYS_TEXT_BASE		= 0x00000000
-PLATFORM_RELFLAGS	+= -ffunction-sections -fdata-sections