common/spi_nor.c: Don't update capacity or page_size after error
common/spi_nor.c: Don't update capacity or page_size after error

If there was an error getting the capacity or page size, don't update
the values with an incorrect/unknown/uninitialized value.

BUG=None
BRANCH=None
TEST=Build all boards successfully.

Change-Id: I907f14f219f721ec9e9753a38e4bf998bbc16324
Signed-off-by: Martin Roth <79230511ccf79da3f7e9e82dbcc9c1ec2f734fa0@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/370665
Reviewed-by: David Hendricks <3b0deacc4b5357f519084f1ea34bd42bf5d34545@chromium.org>
Reviewed-by: Ewout van Bekkum <638f134dbc68778d6b859fb04a64baea2b00b021@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec