arm: mvebu: turris_omnia: Use thumb instructions in SPL to save space

With the latest changes to the drivers (SPI_FLASH_SPANSION etc), Travis
reports that the SPL image is too big. Let's use the thumb instructions
in SPL to save some space and make the image fit again.
Signed-off-by: NStefan Roese <sr@denx.de>
Cc: Baruch Siach <baruch@tkos.co.il>
Cc: Marek Behun <marek.behun@nic.cz>
Reviewed-by: NMarek Behún <marek.behun@nic.cz>

configs/turris_omnia_defconfig

 CONFIG_ARM=y
+CONFIG_SPL_SYS_THUMB_BUILD=y
 CONFIG_ARCH_MVEBU=y
 CONFIG_SYS_TEXT_BASE=0x00800000
 CONFIG_SPL_LIBCOMMON_SUPPORT=y
@@ -7,13 +8,13 @@ CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_TARGET_TURRIS_OMNIA=y
 CONFIG_SPL_SERIAL_SUPPORT=y
 CONFIG_SPL=y
+CONFIG_NR_DRAM_BANKS=2
 CONFIG_DEBUG_UART_BASE=0xd0012000
 CONFIG_DEBUG_UART_CLOCK=250000000
 CONFIG_SPL_SPI_FLASH_SUPPORT=y
 CONFIG_SPL_SPI_SUPPORT=y
 CONFIG_DEBUG_UART=y
 CONFIG_DISTRO_DEFAULTS=y
-CONFIG_NR_DRAM_BANKS=2
 CONFIG_BOOTDELAY=3
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 CONFIG_MISC_INIT_R=y
@@ -40,9 +41,9 @@ CONFIG_ENV_SPI_MAX_HZ=50000000
 CONFIG_SPL_OF_TRANSLATE=y
 CONFIG_SCSI_AHCI=y
 CONFIG_ATSHA204A=y
+CONFIG_DM_MMC=y
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_MV=y
-CONFIG_DM_MMC=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_SPANSION=y
 CONFIG_PHY_MARVELL=y