meta-ibm: Remove unnecessary setting BMC_RW_SIZE

This variable is set to 0x600000 by default in the phosphor layer - no
need to override it again in meta-ibm.

Change-Id: I1b6717dafec89bc12f700091f4b93ecce32a1b69
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-witherspoon/recipes-phosphor/flash/phosphor-software-manager_%.bbappend b/meta-witherspoon/recipes-phosphor/flash/phosphor-software-manager_%.bbappend
index eafd11f..b58fc3b 100644
--- a/meta-witherspoon/recipes-phosphor/flash/phosphor-software-manager_%.bbappend
+++ b/meta-witherspoon/recipes-phosphor/flash/phosphor-software-manager_%.bbappend
@@ -1,7 +1,6 @@
 BMC_RW_MTD = "bmc"
 BMC_RO_MTD = "alt-bmc+bmc"
 BMC_KERNEL_MTD = "bmc"
-BMC_RW_SIZE = "0x600000"
 
 # Enable signature verification by DISTRO_FEATURE obmc-ubi-fs
 PACKAGECONFIG_append_df-obmc-ubi-fs = " verify_signature"