mb/google/nissa/var/xivu: Modify SPI flash to 16M

Follow latest schematic to modify SPI flash to 16M.

BUG=b:236576117
BRANCH=None
TEST=emerge-nissa coreboot

Signed-off-by: Ian Feng <ian_feng@compal.corp-partner.google.com>
Change-Id: I56be68b962c38d3f885dcf25a0251b8d9ab6ff3f
Reviewed-on: https://review.coreboot.org/c/coreboot/+/65446
Reviewed-by: Frank Wu <frank_wu@compal.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: John Su <john_su@compal.corp-partner.google.com>
Reviewed-by: Reka Norman <rekanorman@chromium.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
diff --git a/src/mainboard/google/brya/Kconfig.name b/src/mainboard/google/brya/Kconfig.name
index 92e84c0..6f44e2e 100644
--- a/src/mainboard/google/brya/Kconfig.name
+++ b/src/mainboard/google/brya/Kconfig.name
@@ -253,6 +253,5 @@
 config BOARD_GOOGLE_XIVU
 	bool "->  Xivu"
 	select BOARD_GOOGLE_BASEBOARD_NISSA
-	select BOARD_ROMSIZE_KB_32768
 	select DRIVERS_GENERIC_GPIO_KEYS
 	select DRIVERS_GENESYSLOGIC_GL9750