defconfig: am437x_gp_evm: enable timer driver model

Enable timer driver model for am437x_gp_evm as omap-timer supports
driver model.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

configs/am437x_gp_evm_defconfig

@@ -18,3 +18,5 @@ CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_MACRONIX=y
 CONFIG_SYS_NS16550=y
 CONFIG_TI_QSPI=y
+CONFIG_TIMER=y
+CONFIG_OMAP_TIMER=y